Voltage Follower, 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= ∞ 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.V₀=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.        So V_in is applied to the non inverting input terminal, and the feedback voltage across R₁ devices the inverting input terminal.

3.        This circuit is also called as a current – series negative feedback amplifier.

4. Because the feedback voltage across R₁ (applied Non-inverting terminal) depends on the output current i₀ 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 – 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 V₁ at the non-inverting (+) terminals and

2.        To establish relationship between V₁ and the load current I_L .

So Applying KCL at node V₁ we can write that,