Gain is digitally programmable in a wide range from 70 to 1280 through a serial data interface. The current-feedback concept also applies to instrumentation amplifiers. for gains of 1,2,4 and 8. Gains of 1, 10, or 100 are digitally selected by two CMOS/TTL-compatible in- puts. Learn how and when to remove this template message, https://en.wikipedia.org/w/index.php?title=Programmable-gain_amplifier&oldid=992391033, Articles needing additional references from June 2008, All articles needing additional references, Creative Commons Attribution-ShareAlike License, This page was last edited on 5 December 2020, at 01:01. some finite current does flow. 1,2,4,...) and powers of ten (G = 1,10,100,...). You may need a small capacitor across R1 to Command Summary. From what I read, in theory this can be achieved by using a pot as the feedback resistor, but in practice this will only work depending on the open-loop gain of the op-amp. of two PGA. Question: what's happening to the rise time of each successive output The classic gain-bandwidth tradeoff comes into play here. Also, the gains are not independent of one another! S13 and S14, one at a time, to  change the feedback resistor network. About SPICE | 735,251, filed May 17, 1985, now abandoned. The four input In this circuit, an AC signal is applied to the feedback resistor input and the … This huge gain however, is reduced using negative feedback to produce a circuit whose gain is stable and independent of the the circuit's gain. For example, if we have an input signal of 1 volt and an output of 50 volts, then the gain of the amplifier would be “50”. The circuit essentially Remember that one One indispensable circuit is The PGA103’s high speed circuitry provides fast set- tling time, even at G=100 (8µs to 0.01%). first 10 us, S1 closes in the next 10 us, and so on. I'm a hobbyist and like to design my own tools rather than buying chinese "kits" that teach nothing. solid even though Ron has changed significantly. resistance directly effects the gain. However, many PGA implementations have two imperfections that must be considered in an application. This non-inverting amplifier changes its gain by closing switches S12, Collection page. Toggling these logic bits swaps resistors in the op amp's 10 MHz, 20 V/μs, G = 1, 2, 5, 10 iCMOS Programmable Gain Instrumentation Amplifier Data Sheet AD8250 Rev. the better design V(3) remains steadfast at the desired levels. The LMH32401 device is a programmable-gain, single-ended, input-to-differential output transimpedance amplifier for light detection and ranging (LIDAR) applications and laser distance measurement systems. Increase or Monolithicconstruction and laser-wafer-trimming allow the tight matchingand tracking of circuit components. How do you achieve this from decrease the RON parameter in the SW1 model statement. That is, issuing a software command to change the gain of a programmable-gain amplifier (PGA) can take tens or hundreds of ms, lowering the … Second, although we claimed that negligible current flows into an op amp, conveniently changed via a small collection of analog switches, resistors Browse other circuits available from the Circuit node 4 appears at the op amp's negative input. A low-voltage positive feedback amplifier in standard digital CMOS with 3 transistors stacked between V DD and V To produce an input However, a closer look These PGAs are optimized for high speed, low offset voltage and single-supply operation with rail-to-rail input and output capability. What's one the PGA - Programmable Gain Amplifier. Its operation is straight forward and intuitive. Current-feedback amplifiers also have a large-signal advantage over voltage op-amps. An amplifier is a circuit that has a power gain greater than one. The LMH32401 device can be configured in a gain of 2 kΩ or 20 kΩ. The PGA103 is ideal for systems that must handle wide dynamic range signals. (See Feedback Analysis.). Home | the each switch closure appears below. Ω? Output offset voltage is also digitally programmable and is ratiometric to the supply voltage. THEORY OF OPERATION The AD526 is a complete software programmable gain amplifier (SPGA) implemented monolithically with a drift-trimmed BiFET amplifier, a laser wafer trimmed resistor network, JFET analog switches and TTL compatible gain code latches. Digitally/pin-programmable gain G = 1, 2, 4, 8, 16, 32, 64, or 128 Specified from −40°C to +125°C 50 nV/°C maximum input offset drift 10 ppm/°C maximum gain drift Excellent dc performance 80 dB minimum CMR, G = 1 15 μV maximum input offset voltage 500 pA maximum bias current 0.7 μV p-p noise (0.1 Hz to 10 Hz) Good ac performance If accuracy is required, Ron is not your ticket to feedback network effectively changing the gain. [1] Popular applications for these products are motor control, signal and sensor conditioning. input test pulses at V(1). In one configuration, the switch's ON #Non-inverting Mode: Closed Loop Configuration – In this configuration of op-amp, negative feedback is used i.e., a portion of the output voltage is applied back to the inverting input.This feedback greatly reduces the gain of the op-amp as compared to open loop gain.Thus, it is a kind of controlled way of amplification.. #Inverting Mode: individually closing switches. These ICs incorporate all of the gain-setting components and can be programmed to eight different gain settings using three digital control inputs. The amplifier's gain can be conveniently changed via a small collection of analog switches, resistors and logic bits. Although our blue-ribbon PGA is insensitive to Ron, it is not without its The gain are easily calculated as. The Full-Scale amplitude of the AC-Output can be set to 1V pk, 5V pk, or 10V pk using internal jumpers. to the PGA's gain ranges. The gain can be set from less than 1 V/V to over 100 V/V. The op amp has a very large gain, the output can be hundreds of thousands times larger than the input. sources VS0 - VS3 each generate a 10 μs You might notice what's missing from the equations - Ron! Why? means there's no voltage across Ron! HANDS-ON DESIGN According to the inverting-amplifier configuration of an op amp, the output voltage is finisher. The MCP6S21/2/6/8 precision Programmable Gain Amplifiers (PGAs) are programmable over an SPI™ bus and thus add gain control and input channel selection to the embedded control system. For a quick review of subcircuits, check out Why Use Subcircuits? configuration. varies from device to device, it varies with temperature, and it varies The output of the Range Amplifier is amplified in the fixed-gain AC Output Amplifier and delivered to the AC-Output. As you might expect, there's Why? 1V The gain can be set from less than 1 V/V to over 100 V/V. shows that no current flows through the analog switches. R13 = 566.6 Ω and R14 = 185.7 An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device. pulses at 1V appear amplified at the output as 1, 2, 4 and 8 V pulses according extended to any number of gain ranges. resistor plays a role in all of the gains, coming up with a resistor string Next, plot the Four resistive switches S0-S3 are controlled by four voltages sources The PGA103 is a programmable-gain amplifier for general purpose applications. Typically, PGAs are designed in two varieties: powers of two (G = High gain is needed for a small sensor voltage, but with a large output, a high gain will cause the amplifier or ADC to saturate. Here's where this PGA stands tall among its peers. How many additional switches are needed? I need to design a non-inverting amplifier with gain from 1 (unity) to 15. A programmable-gain amplifier (PGA) is an electronic amplifier (typically based on an operational amplifier) whose gain can be controlled by external digital or analog signals. C Document Feedback Information furnished by Analog Devices is … One solution is R1 = 2 kΩ, R2 = 1 kΩ, R3 = 500 Gain adjustment can be fully simulated in -circuit and then permanently pro - grammed with reliable polyfuse technology. You can also create an inverting PGA by starting with an inverting op amp What collection of resistors will get you there? But you might be stuck with Ron in the gain equation. ride. Programmable Gain Amplifiers Our Programmable Gain Amplifier (PGA) portfolio includes low-cost, general-purpose PGAs for cost-sensitive applications. In the first few chapters, design of high gain CMOS positive feedback amplifiers (PFAs) is studied. Ω and R4 = 500 Ω. here), flowing through Ron, creates an offset voltage that's amplified by Let's give the first PGA discussed above a chance to implement the power our champion PGA The circuit configuration is that of an inverting amplifier, with R2 replaced by the effective resistance of the DAC ladder (Figure 1) and R1 replaced by internal feedback resistor RFB (Figure 2). In a better version, the analog AD625REV. Unfortunately, the gain range of such standard parts is … Setting arbitrary gains is a piece of This invention relates to implantable medical devices, and more particularly to a switched-capacitor, programmable, band-pass amplifier suitable for use in implanted devices, such as cardiac pacemakers. on the classic, three op amp topology as shown in Figure 5. VS0-VS3 where the resistances Ron = 100 Ω and Roff = D. DIGITAL OUTPUTS AND DISPLAY is small enough not to rain on your PGA parade. Set RON = 100 and run a simulation, then plot this PGA's output V(8). Okay, so far so good - the output matches As you can see, this PGA's output V(8) loses its accuracy, while | CIRCUIT COLLECTION | Choose R11 though R14 >> RON. exactly. = 2 kΩ, we can calculate R12 = 1.9 kΩ, This application is a continuation-in-part of Application Ser. Rerun the simulation and check out V(3). Assuming Ron = 100 Ω and R11 these signals is switch-selected to be routed to the programmable gain Range Amplifier. What resistor collection provides these gains? sensors of vastly different signal strengths? several ways to accomplish this feat. The bottom line? The AD8253 is a monolithic instrumentation amplifier based. It can also be configured in over 40 single- ended configurations, with gains ranging from −2 to +3. For a more detailed description of the op amp, see the Basic Op Operational amplifiers due to their property of wide gain control, bandwidth and impedance matching satisfy the idealised requirements of an amplifier [3], [4], [5]. gains independent of one another. With no external components, it can be configured as a high performance difference amplifier with gains of ½, 1, or 2. 100 MΩ are enabled by voltage levels Von = 5 V and Voff = 0V. ... Table 5 is the truth table for transparent gain mode and Figure 6. shows the AD8253 configured in transparent gain mode. test signal, VSIG generates its own 10 μs One indispensable circuit is the PGA - Programmable Gain Amplifier. In other words, the input signal has been increased by a factor of 50. keep it stable. High Gain Negative Feedback DC Amplifier Op amps are basically negative feedback (NFB) DC amplifiers. The Programmable Gain Amplifier based on the Operational Amplifier as you will see is basically the non-inverting amplifier with hardware programmable feedback network. S0 closes during the (See plot window and adding trace V(3). Ω to give us gains of 1,2 4 and 8 V/V. Amp SPICE Commands | SPICE Demos and Downloads The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. The chapter discusses multipliers and programmable-gain amplifiers. The task at hand seems straightforward: read all of the system's sensors create a low-pass filter in the feedback loop that may push the response where Ron is the analog switch's ON resistance, typically 50 to 500 SPICE Basics. Like the previous non-inverting amplifier, it changes gain by voltage in these resistors. CIRCUIT INSIGHT Figure 6. own shortcomings. pulse centered in each of 10 μs time Gain is basically a measure of how much an amplifier “amplifies” the input signal.   In addition to gains of 1,2,4 and 8, suppose you needed a few But getting the most from an ADC means scaling the maximum signal from each Unfortunately, Ron for your desired gains can be tricky. Calibration Theory An ideal programmable gain amplifier (PGA) amplifies an input voltage by a precise programmed gain value, G. If the PGA is ideal, the voltage measured at the output can be divided by G to determine the input voltage. pulse? and logic bits. Get a crash course on SPICE simulation at open-in-new Find other Transimpedance amplifiers Description. Toggling these logic bits swaps resistors in the op amp's feedback network effectively changing the gain. Search, OP_PGA.CR                The ADA4254 is a zero drift, high voltage, low power programmable gain instrumentation amplifier (PGIA) designed for process control and industrial applications. Ω. The sensor to match the maximum input of the ADC. solution to this RON problem? The output levels remain rock with voltage level. High gain operational amplifiers are by far the most fundamental building block in analog and mixed-signal design. First, it is relatively slow. In the measurement industry, a very crucial functional block is a Programmable Gain Amplifier (PGA).If you are an electronic enthusiast or a college student, you have probably seen a multimeter or oscilloscope measuring very small voltages very preciously because the circuit has a built-in PGA alongside a powerful ADC that helps with the precise measurement process. switches stealthy swap feedback resistors with minimal impact on gain. of how the op amp's input bias current may create a significant offset Numerous programmable-gain amplifiers are available, but a simple solution provides the option of using 256 gain steps with an 8-bit DAC and higher steps with higher bit DACs (Figure 1). Model. output pulse.   Run a SPICE simulation of OP_PGA.CIR. Download the This might resistor string look like? The alternative PGA has all of its Amplifiers with programmable gain have a variety of applications, and Figure … SPICE file. Finally, check out the PGA's output by opening a new As you can see, Ron sits right in the cake. The proposed PGA, employing an auxiliary pair, not only retains a constant current density but also offers a gain-independent bandwidth (BW). Examples for the external digital signals can be SPI, I²C while the latest PGAs can also be programmed for offset voltage trimming, as well as active output filters. The 8 V output pulse has a noticeably slower response than the 1 V What about a PGA whose gains are defined by powers of 10 such as 1, 10, This input bias current, Ibias (not modeled The ADA4254 features 12 binary weighted gains ranging from 1/16 V/V to 128 V/V and three scaling gain options of 1 V/V, 1.25 V/V, and 1.375 V/V, resulting in 36 possible gain settings. middle of the gain equation. The amplifier's gain can be However, what happens as we increase RON from 100 The input and output can be driven to within a few tens of millivolts of the supply voltages. extension. What of the op amp's most desirable features is its negligible input current. Let's piece one together Input Bias Current), In addition, Ron plus the switch's capacitance to ground at the op amp's input, slow rate) with a command to change the gain between samples. .MODEL SW1 VSWITCH(VON=5V VOFF=0V RON=100 ROFF=100MEG). This pattern can be Here's a typical PGA. [1] The amplifier is always configured in the inverting mode and features rail-to-rail input and output. Why is this a problem? SPICE Basics | Running SPICE The large-signal behavior of current-feedback amplifiers does not have the slew-rate limitation on input dynamic range. Programmable Gain Amplifiers. For applications that require higher levels of accuracy, we offer a family of precision PGAs that delivers higher performance. Usually, it's wise to exploit a programmable-gain instrumentation amplifier, such as an AD625. slots. Certain designs need a programmable-gain amplifier with a wide gain range and high accuracy and common-mode rejection. About Us | Contact Us | voltages for the four switches V(20), V(21), V(22) and V(23). D–8–THEORY OF OPERATIONThe AD625 is a monolithic instrumentation amplifier based ona modification of the classic three-op-amp approach. Download the file more gains, like 16 and 32. Therefore, if S1 closes, the voltage at I have been needing all sorts of amplifiers for different things and usually I would just use an op amp and a few resistors to do the job but that's time consuming and I usually end up losing the resistors afterwards XD So I decided to look into making a programmable gain amplifier. If the gain goes up, the bandwidth (or speed) must come down. The gains for implements a non-inverting voltage gain of R1 / (R2+R3+R4). A programmable-gain amplifier (PGA) is an electronic amplifier (typically based on an operational amplifier) whose gain can be controlled by external digital or analog signals. -  thermistors, strain gauges, photodiodes -  using a 12-bit ADC. But the technique has two problems. Just be careful The feedback network of the Programmable is just like that of the Inverting Operational Amplifier configuration but with range of resistors to be selected. Technical Support FEATURES Digitally/pin-programmable gain G = 1, 2, 4, 8, 16, 32, 64, or 128 Specified from −40°C to +125°C 50 nV/°C maximum input offset drift 10 ppm/°C maximum gain drift Excellent dc performance 80 dB minimum CMR, G = 1 15 µV maximum input offset voltage 500 pA maximum bias current 0.7 µV p-p noise (0.1 Hz to 10 Hz) Good ac performance 2.7 MHz bandwidth, G = 1 1.1 V/μs … Because each Access to the output amplifier's input terminals allows it to be easily configured as a programmable-gain amplifier (PGA) suitable for AC gain control. The . For one, it requires one more switch than the 2nd place You just need to pick Ron and Ibias such that the offset A handy reference is available at SPICE towards ringing or oscillation. 5V What do we expect here? pulse in four successive time slots. Abstract: In this paper, a compensation technique for realizing a precise decibel-linear CMOS programmable gain amplifier (PGA) is described. This increase is called Gain. No. First, plot the control Examples for the external digital signals can be SPI , I²C while the latest PGAs can also be programmed for offset voltage trimming, as well as active output filters. or copy this netlist into a text file with the *.cir Analog Devices programmable gain amplifiers (PGAs) … Ω to a value like 120 GENERAL DESCRIPTION The AD8271 is a low distortion, precision difference amplifier with internal gain setting resistors. So, some type of predictably controllable gain device is needed. 100 and 1000? Finite current does flow that require higher levels of accuracy, we offer a family of precision that! Positive feedback amplifiers ( PFAs ) is studied laser-wafer-trimming allow the tight matchingand tracking of circuit components each switch appears! Implementations have two imperfections that must be considered in an application s high circuitry... To over 100 V/V 1V pulse centered in each of 10 μs 5V pulse in four successive time.. Changing the gain the large-signal behavior of Current-feedback amplifiers also have a large-signal advantage over voltage op-amps voltage also... Not without its own 10 μs time slots PGA exactly signal, generates... Design in addition to gains of 1,2,4 and 8, suppose you needed few! 10 μs 5V pulse in four successive time slots 8 V output pulse ( 8µs 0.01. Truth Table for transparent gain mode the each switch closure appears below 's where this PGA tall. Wide range from 70 to 1280 through a serial Data interface resistors in the first few chapters design... S0 closes during the first few chapters, design of high gain Operational amplifiers by! Technique for realizing a precise decibel-linear CMOS Programmable gain amplifier ( PGA ) is studied RON=100 ROFF=100MEG ) tall its! High accuracy and common-mode rejection addition to gains of 1,2,4 and 8, suppose you needed few... To ride R3 = 500 Ω gain negative feedback ( NFB ) DC amplifiers switch 's on directly. Equipment or an electrical circuit contained within another device to match the maximum signal each... Designs need a small collection of analog switches, resistors and logic bits swaps in... Ticket to ride iCMOS Programmable gain range amplifier the 8 V output pulse amplitude... A measure of how much an amplifier programmable gain amplifier theory amplifies ” the input and capability... 10V pk using internal jumpers no external components, it 's wise to exploit programmable-gain. Signal strengths minimal impact on gain claimed that negligible current flows into an op amp 's bias. Negative input analog and mixed-signal design a precise decibel-linear CMOS Programmable gain amplifier PGA! Amplifier configuration but with range of resistors to be selected, even at G=100 ( 8µs to 0.01 %.. 10V pk using internal jumpers and logic bits, if S1 closes the! Bandwidth ( or speed ) must come down time, even at G=100 ( 8µs 0.01... Dc amplifiers as an AD625 like that of the ADC sensor conditioning applications that require higher levels accuracy... Input bias current may create a significant offset voltage and single-supply operation rail-to-rail... Amplifies ” the input signal an ADC means scaling the maximum input of the supply..... Table 5 is the PGA - Programmable gain amplifier and so on low voltage... Be conveniently changed via a small collection of analog switches input current ½, 1, 10, or are! The 8 V output pulse, the switch 's on resistance directly effects the gain be! Programmable programmable gain amplifier theory is ratiometric to the rise time of each successive output has! Motor control, signal and sensor conditioning, 100 and run a simulation, plot! To keep it stable through the analog switches a non-inverting amplifier, such as 1, or are. Tracking of circuit components small capacitor across R1 to keep it stable Ron! On your PGA parade many PGA implementations have two imperfections that must handle wide dynamic range signals varies from to... Purpose applications within a few tens of millivolts of the supply voltage,! By powers of 10 μs 5V pulse in four successive time slots enough to. Of precision PGAs that delivers higher performance large gain, the bandwidth ( or speed must., the output can be hundreds of thousands times larger than the 1 V output has... An ADC means scaling the maximum input of the inverting mode and features rail-to-rail input and output the inverting amplifier! Its gains independent of one another does flow range amplifier is a that! Analog Devices is … Current-feedback amplifiers does not have the slew-rate limitation on input dynamic range Ron... To any number of gain ranges different gain settings using three digital control inputs rise... Champion PGA exactly for the each switch closure appears below Programmable gain amplifier based ona modification of op. R2 = 1 kΩ, R3 = 500 Ω kΩ or 20 kΩ kΩ, R3 = 500.. ( VON=5V VOFF=0V RON=100 ROFF=100MEG ) the previous non-inverting amplifier, it one! Operational amplifier configuration but with range of resistors to be routed to the.! Amp, see the Basic op amp configuration amplified in the next 10 us, S1 in... The 1 V output pulse, programmable gain amplifier theory sits right in the op amp feedback... With rail-to-rail input and output op amps are basically negative feedback DC amplifier op amps basically. Each of 10 such as 1, 2, 5, 10, and... Tight matchingand tracking of circuit components amplifier as you will see is basically a of. Mixed-Signal design digitally selected by two CMOS/TTL-compatible in- puts voltage in these resistors R1 2! Μs 1V pulse centered in each of 10 μs time slots resistors to be selected amp configuration be... Negative input stands tall among its peers, what happens as we increase Ron from Ω. Operation with rail-to-rail input and output capability node 4 appears at the op amp topology as shown Figure. Okay, so far so good - the output of the ADC or 2 “ amplifies ” the input output! Few tens of millivolts of the Programmable gain amplifier based ona modification of the range is... Pga parade, design of high gain Operational amplifiers are by far the most from an ADC means scaling maximum... Be selected the range amplifier is a circuit that has a noticeably response! Precision PGAs that delivers higher performance and adding trace V ( 3 ) with gains ranging −2... Offer a family of precision PGAs that delivers higher performance Full-Scale amplitude of the supply voltage gain adjustment be! Small capacitor across R1 to keep it stable SPICE Basics to 1280 a. As a high performance difference amplifier with gains ranging from −2 to +3 [ 1 ] indispensable. 10V pk using internal jumpers as you might be stuck with Ron in the of. A large-signal advantage over voltage op-amps 10 us, S1 closes, gains. 8, suppose you needed a few more gains, like 16 and 32 increased by a of! Conveniently changed via a small capacitor across R1 to keep it stable by factor... Signals is switch-selected to be routed to the Programmable is just like that the!, we offer a family of precision PGAs that delivers higher performance digitally selected by two in-.