SDIY Building Blocks

Appearance

Voltage Amplifiers ​

What It Does

Amplifiers increase the amplitude of a signal (multiplication).

Inverting amplifier ​

Formula

Gain = -1 * R2/R1

Basic op-amp ​

  • The inverting amplifier can both amplify and attenuate voltage levels.
  • Amplification when R2 > R1.
  • Attenuation when R1 > R2.
  • The signal will always be inverted. Sometimes this is useful, and sometimes not. To correct the signal You often see two inverting amplifiers in series.
  • Please play with different resistor values in the simulator.

Attention

Please be careful with any circuitry before the input resistors of the inverting op-amp !! If you add other resistors before "R1" these components will become part of a resistor network the op-amp uses to "calculate" its amplification !

With potentiometer ​

Replace fixed resistor values with potentiometers to get more live control over your circuits.

  • Notice the potentiometer is placed inside the feedback path.
  • If you add any resistor before the potentiometer you set the maximum amplification.
  • If you add any resistor after the potentiometer you set the minimum amplification.

Non-inverting amplifier ​

If you don't want to have inverted signals you can also use the "non-inverting amplifier". However notice the +1 in the formula. Because of this the minimum amplification is minimal 1:1.

Formula

Gain = 1 + R2/R1

Basic op-amp ​

  • Advantage of the non-inverting amplifier:
    • No signal inversion.
    • Resistors before the input of the non-inverting amplifiers have no effect on the amplification (in contrary to the inverting op-amp).
  • I find the inverting op-amp nevertheless often more flexible for projects, because it also allows you to attenuate signals to 0V.

With input attenuator ​

A little trick to get also both larger and smaller gain values (attenuation) from your non-inverting amplifier is to add a potentiometer before the input.

Formula

Gain = (1 + R2/R1) / attenuation

  • Notice the potentiometer is just placed before the op-amp.
  • Set the resistor values for the max amplification.
  • Use the potentiometer to get an amplification between 0V and Max.

Differential amplifiers ​

The output of the differential amplifier is determined by the difference between the two input voltages. If both input voltages are the same and in phase the output of this configuration is zero.

Basic ​

Formula

Vout = -R2/R1 * (Vin2 - Vin1)

Formula (R1=R3, R2=R4)

Gan = (Vin2 - Vin1) * R2/R1

  • Notice: Vin1 - Vin2 = 3V.

Attenuverter ​

  • Please play with the potentiometer and see how the signal inverts and attenuates.

Wheatstone bridge ​

With a wheatstone bridge you can detect small differences in resistance. Great for resistance based sensors.

  • Notice the two parallel voltage dividers.
  • Notice 0V at the output when all the resistor values inside the wheatstone bridge are the same.
  • Please change a resistor value inside the wheatstone bridge a bit and notice the ouput voltage going up.
  • Notice the differential amplifier. Increase its amplification to detect smaller changes in resistance.