Biasing non-inverting op amp using split resistor tutorial 4 | applied electronics engineering

# Biasing non-inverting op amp using split resistor tutorial 4

By Applied Electronics - Tuesday, April 4, 2017 No Comments
In this op amp biasing tutorial you will learn how to bias a non inverting op amp using split resistor technique. In earlier tutorial how to bias a non-inverting op amp - tutorial 3 we showed you how to bias an op amp using voltage divider biasing technique.

The process of designing the biasing circuit follows similar to the voltage divider biasing upto the determination of the gain and dc offset voltages which in terms of straight line are equation are slope and intercept respectfully. See the tutorial Biasing op amp for output voltage range using straight line method - tutorial 2 for more on this. It is similar to transistor biasing, see Voltage Divider Biasing Circuit Analysis using Proteus. For biasing transistor an excellent book to read is Electronic Principles 8th Edition by Albert Malvino & David Bates.

Beginning with input voltage range and output voltage range, we write down two equations and solve for the value of slope and intercept. Then using these values we determine the resistor values for the biasing circuit. But before determining the resistors we have to first to know the circuit diagram.

Continuing our last tutorial example, we have input voltage range -0.2V to 0.2V and output voltage from 0.5V to 2.5V. Using straight line equations we solved the value of Gain or slope as 5 and DC offset or intercept as 1.5V.

Once we have the gain and slope we now show the split resistor biasing of an non-inverting amplifier. This is as shown below.

This is same circuit as voltage divider biasing. The only difference is that there is no extra resistor in the voltage divider biasing circuit formed here by R3 and R4 and also there is no decoupling capacitor in the voltage divider biasing sub-circuit. Thus in split resistor biasing one of the input terminal, non-inverting terminal in this case, is biased to desired DC offset by splitting the power supply at the terminal. Here R3 and R4 resistors does this job and are called the split biasing resistors.

The calculation of these resistors was shown in the earlier tutorial how to bias a non-inverting op amp - tutorial 3. It is also assumed that the reader know how to calculate the coupling and decoupling capacitors. See How to calculate Coupling Capacitor? Coupling Capacitor Formula for in-details.