Purpose of Voltage Follower ?
Purpose of Voltage Follower ?
A voltage follower (also
called a unity-gain amplifier, a buffer amplifier, and an isolation
amplifier) is a op-amp circuit which has a voltage gain of 1.
This means that the op amp does not provide any amplification to the
signal. The reason it is called a voltage follower is because the output
voltage directly follows the input voltage, meaning the output voltage
is the same as the input voltage. Thus, for example, if 10V goes into
the op amp as input, 10V comes out as output. A voltage follower acts as
a buffer, providing no amplification or attenuation to the signal.
What is the Purpose of a Voltage Follower
An op amp circuit is a circuit with a very high input
impedance. This high input impedance is the reason voltage followers are
used. This will now be explained.
When a circuit has a very high input impedance, very
little current is drawn from the circuit. If you know ohm's law, you
know that current, I=V/R. Thus, the greater the resistance, the less
current is drawn from a power source. Thus, the power of the circuit
isn't affected when current is feeding a high impedance load.
Let's look at both illustrations below:
The below circuit is a circuit in which a power source feeds a low-impedance load.
In this circuit above, the load demands and draws a huge amount of
current, because the load is low impedance. According to ohm's law,
again, current, I=V/R. If a load has very low resistance, it draws huge
amounts of current. This causes huge amounts of power to be drawn by the
power source and, because of this, causes high disturbances and use of
the power source powering the load.
Now let's look at the circuit below, connected to an op-amp voltage follower:
This circuit above now draws very little current from the power source
above. Because the op amp has such high impedance, it draw very little
current. And because an op amp that has no feedback resistors gives the
same output, the circuit outputs the same signal that is fed in.
This is the reason voltage followers are used. They draw very little
current, not disturbing the original circuit, and give the same voltage
signal as output. They act as isolation buffers, isolating a circuit so
that the power of the circuit is disturbed very little.
Voltage followers are important to buffer or isolate a low impedance
load from a voltage source. This means that rather than connect a
relatively low value of load resistance across the terminals of the
power source, the op amp can be used to eliminate any loading that might
occur. Thus, the power source will not be loaded down. The circuit acts
as an ideal voltage source with nearly zero internal impedance, since
it barely uses any current, yet outputs the full voltage.
Inverting amplifier and non-inverting amplifier both are negative feedback op-amp circuits
Non-inverting amplifier the input signal is applied to non-inverting pin
Inverting amplifier the input signal is applied to the inverting pin
Voltage follower is a negative feedback op-amp circuit with unity gain
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