## Voltage follower

Table of Contents

**Voltage **F**ollower**, **Voltage to Current Converter with floating loads (V/I)**, **Voltage to current Converter with Grounded load**

**Voltage Follower**

In the Non-inverting Amplifier Configuration, if R1= âˆž and Rf=0. The Amplifier functions as a voltage Follower or Unity-gain Amplifier.

That is

The circuit consist of an op-amp and a wire connecting the output voltage to the input ,i.e the output voltage is equal to the input voltage, both in magnitude and phase.V_{0}=V_{i}

The circuit is known as a voltage follower because its output voltage follows its input voltage. It provides very low output impedance and extremely high input impedance of the order of M. As a result, this circuit uses very little source current. So For impedance matching applications, the voltage follower can be used as a buffer between a high impedance source and a low impedance load.

**1. Voltage to Current Converter with floating loads (V/I)**

1. Voltage to current converter in which load resistor R_{L} is floating (not connected to ground).

2.Â Â Â Â Â Â Â Â So V_{in}Â is applied to the non inverting input terminal, and the feedback voltage across R_{1}Â devices the inverting input terminal.

3. This circuit is also called as a current â€“ series negative feedback amplifier.

4. Because the feedback voltage across R_{1} (applied Non-inverting terminal) depends on the output current i_{0} and is in series with the input difference voltage V_{id}

So From the fig input voltage Vin is converted into output current of Vin/R1 [Vin ->i0 ] . In other words, input volt appears across R1. So If R1 is a precision resistor, the output current (i0 = Vin/R1 ) will be precisely fixed.

**Voltage follower Applications:**

1. Low voltage ac and dc voltmeters

2. Diode match finders

3. LED

4. Zener diode testers.

**2. Voltage to current Converter with Grounded load**

This is the other type V â€“ I converter, in which one terminal of the load is connected to ground.

**Analysis of the circuit:**

The analysis of the circuit can be done by following 2 steps.

1. To determine the voltage V_{1} at the non-inverting (+) terminals and

2. To establish relationship between V_{1} and the load current I_{L} .

So Applying KCL at node V_{1}Â we can write that,