Using the equivalent representation shown fig

( )V1 R1

	(a)		(b)
	Figure 14.16
EXAMPLE 14.4

Solution

R 5 0 0 k�

620	Chapter 14	Operational Amplifiers


Figure 14.17

Probably the most used of the op-amp circuits is the summing amplifier circuit shown in Fig. 14.18a. The circuit shows a three-input summing amplifier circuit, which pro-vides a means of algebraically summing (adding) three voltages, each multiplied by a constant-gain factor. Using the equivalent representation shown in Fig. 14.18b, the output voltage can be expressed in terms of the inputs as

Figure 14.18

(a) V1 � �1 V, V2 � �2 V, V3 � �3 V, R1 � 500 k�, R2 � 1 M�, R3 � 1 M�. (b) V1 � �2 V, V2 � �3 V, V3 � �1 V, R1 � 200 k�, R2 � 500 k�, R3 � 1 M�.		EXAMPLE 14.5	621
14.4		EXAMPLE 14.5	621