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Amplifier Circuits:  Variable Gain
Amplifier -- Main Page

Variable Gain Amplifiers:  #'s - K      L - Z
 

Last Updated: October 13, 2017 03:06 AM

Circuits Designed by Dave Johnson, P.E. :

Variable Isolated AC Voltage Spans 0VAC to 280Vac -  I designed and built this circuit about 25 years ago.  It came in handy for many projects that were powered from 120 VAC, 240 VAC and 277 VAC.  It provides complete isolation from the power line.  It uses two 1:1 isolation transformers that are wired in parallel. . . Circuit by Dave Johnson P.E.-July 8, 2000

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

LM317 variable Power Supply -  A truly timeless circuit.  LM317 is a versatile and highly efficient 1.2-37V voltage regulator that can provide up to 1.5A of current with a large heat sink.  It's ideal for just about any application. __ copy of geocities.com/tomzi.geo page

Low Noise AC Amplifier with Programmable Gain & Bandwidth -  Two LTC6910 programmable gain amplifiers can be combined to provide independent gain and bandwidth control using two 3 bit digital words.  The Gain Control PGA simply varies the circuit gain from 1 to 100.  The Bandwidth Control PGA puts signal gain inside the feedback loop of the amplifier.  As this gain is increased the effective value of feedback resistor R2 is decreased.  This pushes out the upper low pass corner frequency of the ac amplifier. __ Linear Technology/Analog Devices App Note, Mar 16th 2010

Micropower Buffered Variable Voltage Source -  Circuit Ideas for Designers App Note __ Advanced Linear Devices, Inc

One IC Provides Gains of 10 & –10 -  08/07/03  EDN-Design Ideas Real-world data-acquisition systems require amplifying weak signals to match the full-scale input range of an A/D converter.  Unfortunately, when you configure them as gain blocks, most common amplifiers have both gain errors and off__ Circuit Design by Moshe Gerstenhaber and Charles Kitchin, Analog Devices, Wilmington, MA

Programmable Gain Amplifier (Single Supply) -  The CMOS switch selects which feedback node is used, thus setting the loop gain to different levels as desired.  The advantage of this circuit is that the capacitance and leakage effects are isolated from the feedback resistors so accuracy is maintained.  The deselected opamp sections saturate, but remain well behaved with the LT1079. __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Programmable Gain Amplifier, using the MAX532 DA - C -  App Note/ 301 / Mar-08 __ Maxim Integrated

Programmable-gain Amp achieves high gains -  EDN-Design Ideas 10/22/2015    Roll your own PGA to get the exact high gains you need__ Circuit Design by Carlos Castro-Miguens & Jose Castro-Miguens

Simple Circuit Fixture Statically Tests Programmable-Gain Amplifiers -  06/26/08  EDN-Design Ideas Using a simple fixture having a common ground point, you can statically test digital gain-programmable amplifiers__ Circuit Design by Marián Štofka, Slovak University of Technology, Bratislava, Slovakia

Simple Circuit variable frequency oscillator -  This is a very simple circuit utilising a 555 timer IC to generate square wave of frequency that can be adjusted by a potentiometer.

Simple Circuit Variable Voltage Source -  The high current regulator below uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency.  For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage.  The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the (0.1ohm) equalizing resistors (1volt at 10 amps) , so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage __ Designed by Bill Bowden

Single IC Provides Gains Of 10 & –10 -  7-Aug-03 EDN-Design Ideas Real-world data-acquisition systems require amplifying weak signals to match the full-scale input range of an A/D converter.  Unfortunately, when you configure them as gain blocks, most common amplifiers have both gain errors and offset drift.  The typical two-resistor gain-setting arrangement found in many op-amp circuits has serious accuracy and drift limitations__ Circuit Design by Moshe Gerstenhaber and Charles Kitchin, Analog Devices, Wilmington, MA

Single Supply Video Line Driver (AC Coupled) -  When AC-coupling video, the waveform Dynamics change with respect to the bias point of the amplifi er according to the scene brightness of the video stream.  In the worst case, 1VP-P video (composite or Luminance + Sync in Y/C or YPBPR format) can exhibit a varying DC content of 0.56V, with the dynamic requirement being __ Linear Technology/Analog Devices App Note, Mar 25th 2010

Synthesize Variable Resistors with Hyperbolic Taper -  8-Jan-09 EDN-Design Ideas A simple circuit produces a ground-reference variable resistance with a hyperbolic-control characteristic__ Circuit Design by TL Flaig, Clinton, WA

Variable Gain Control Produces Pure Sine Wave -  10/27/94 EDN-Design Ideas The circuit in Fig 1 delivers a pure, buffered, and level-controlled sine wave.  With no tuning requirements, the circuit works with all crystals up to about 30 MHz.   __ Circuit Design by Barry Harvey, Elantec Corp, Milpitas, CA

Variable Isolated AC Voltage Spans 0VAC to 280Vac -  I designed and built this circuit about 25 years ago.  It came in handy for many projects that were powered from 120 VAC, 240 VAC and 277 VAC.  It provides complete isolation from the power line.  It uses two 1:1 isolation transformers that are wired in parallel. . . Circuit by Dave Johnson P.E.-July, 2000

Variable Voltage Regulator -  As Ron suggests, controlling the output voltage from a regulator can be made variable in three ways __ Designed by Ron J.

Variable-gain stage uses voltage-output DA - C -  08/01/97 EDN-Design Ideas A voltage-output DAC normally generates an output voltage that is a fraction of the input-reference voltage.  In many designs, however, it is necessary to multiply the input voltage by a programmable gain, or, in other words, to create a variable-gain stage.  You can easily implement a variable-gain stage using a low-cost voltage-output DAC__ Circuit Design by Eugene Palatnik, BCI International, Waukesha, WI

Wideband Digitally Programmable Gain Amplifier -  The LTC6910 is a CMOS programmable gain (from 0 to 64) amplifier.  The amplifiers provide for a differential input signal and for dc biasing the output into a precise voltage reference based level in a single supply design. __ Linear Technology/Analog Devices App Note, Mar 16th 2010


Variable Gain Amplifiers:  #'s - K      L - Z

 


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