Variable Voltage Amplitude

This circuit allows control over the voltage amplitude. This is achieved by using a Non-Inverting Op-Amp configuration. (Inverting Configuration will also work, but it will cause a phase shift and inversion) The feedback resistor Rf is replaced by a potentiometer, which gives control over the gain. The gain equation for a Non-Inverting Configuration is: 1+Rf/Ri In our example, the circuit is designed to have a max gain of 2: 1 + 10k/10k = 1+ 1 = 2 If a higher gain is needed, Ri should be reduced. Remember that we are limited to the power rail supply voltage of the op-amp. If the gain is too high, the output will slam towards the positive rail. We are using a LM358 op-amp which has a voltage drop of 1.5v from the rail voltage. Supply voltage = 15V Max output Voltage = 15V - 1.5V = 13.5V Since our circuit is designed to have a max gain of 2, the max output voltage for this circuit is 10V.