Chapter 8
Exercise 8:
Hint: For b) consider the maximum value of numerator and minimum value of denominator.

Ans: 27.5 is the nominal gain, negative because it is inverting amplifier. Because of the 10% uncertainy in resistors, the magnitude of gain can swing from 22% increase to 18% decrease.

Exercise 13:
Hint: Gain is 1 + R_f / R₂

Ans: dc part is 2.46 V and the oscillating part is 0.123 V.

Exercise 16:
Hint: The R₂ : R₄ voltage divider holds the non-inverting input at a fixed voltage.

Ans: 27.4 mV

Exercise S8-2:
Hint: The Thévenin resistance will change the effective value of the input resistance in the inverting configuration.

Ans:
a. R_f / R_i = 100. For example, R_i = 1k and R_f = 100k.

b. R_f / R_i = 99.

c. For the noninverting configuration, the effective input impedance is extremely high and does not load the transducer. There is no change in the gain.

For the inverting configuration, the effective input impedance is the sum of R_i and R_TH. If R_i = 10k (and R_f = 1.0M) then the effective gain is 16.7. As R_i decreases, the effective gain approaches 20.

To eliminate loading effects or changes in gain when using an inverting configuration, use a voltage follower between the transducer and the inverting stage.