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Activity: Variable Gain Amplifiers

Objective:

In this laboratory we continue our discussion on operational amplifiers (see the previous lab here: Activity 1. Simple Op Amps) focusing on variable gain / voltage-controlled amplifiers.

Most operational amplifier or op-amp circuits have a fixed level of gain. However it is often useful to be able to vary the gain. This can be done simply by using a potentiometer on the output of a fixed gain op-amp circuit, but sometimes it may be more useful to vary the actual gain of the amplifier circuit itself.

A variable-gain or voltage-controlled amplifier is an electronic amplifier that varies its gain depending on a control voltage. This type of circuit has many applications, including audio level compression, synthesizers and amplitude modulation. It can be realized by first creating a voltage-controlled resistor, which is used to set the amplifier gain. The voltage-controlled resistor is one of the numerous interesting circuit elements that can be produced by using a transistor with simple biasing. Another approach is to use potentiometers to vary the value of the resistors that set the gain of the amplifier.

university/courses/electronics/electronics-lab-variable-gain-amplifier.1522053556.txt.gz · Last modified: 26 Mar 2018 10:39 by amiclaus