0195136047.pdf

264 ANALOG BUILDING BLOCKS AND OPERATIONAL AMPLIFIERS

*5.4.1An op amp has a finite gain of only 50, but is
otherwise ideal. For the inverting-amplifier circuit
of Figure 5.4.1, ifR 2 =20 k, what value ofR 1
would be needed to give a gain of−15? If the op
amp’s gain could be increased by 20%, find the
new gain.
5.4.2Consider an inverting-amplifier circuit with posi-
tive noninverting input, as shown in Figure P5.4.2
with values. Obtainvo.
5.4.3LetvSin Problem 5.4.2 be a sine wave of peak
voltage 3 V. Sketchvo. Rework the problem with

R 2 =40 kinstead of 30 k, and sketchvo.

5.4.4Consider the op-amp circuit of Figure P5.4.4.

Sketch the waveforms ofvSandvo,ifvSis a

sinusoidal voltage source with a peak value of 2 V.

5.4.5In the ideal inverting summing amplifier circuit

(see Figure 5.4.3) with two inputs, forRf =

10 k, findR 1 andR 2 so thatvo=− 10 vi 1 − 5 vi 2.

5.4.6Consider Figure 5.4.4 of the noninverting sum-

ming amplifier. LetRm=(m+ 0. 5 ) 50 , m=

1 , 2 , 3 ,4, and 5. Also letRd= 50 andRf =

3k. Findvo.

−

+

+

−

R 2

A(ω) A(ω)

H 1 (ω)

x(t)

y(t)

R 2

R 1

x(t) y(t)

R 1

Σ

+

−

H 1 (ω) =

H 2 (ω)

Ao

I + j(ω/ωh)

Input

x(t)

Forward network

Feedback network

xe(t)

xf(t)

y(t)

output

Σ

H 2 (ω) =RR^1

1 +^ R 2

Figure P5.3.5

−

+ vo

vS = 3 V

1 V

R 2

R 1

A

B

i

i

30 kΩ

+15 V

−15 V

10 kΩ

Figure P5.4.2

−

+

vo

vS

(2 V peak)

1.5 V

R 2

R 1

A

B

2 MΩ

+10 V

−10 V

1 MΩ

Figure P5.4.4