0195136047.pdf

262 ANALOG BUILDING BLOCKS AND OPERATIONAL AMPLIFIERS

*5.2.9Consider the noninverting amplifier of Example
5.2.2. LetRi=1kandRf=2k. Let the op
amp be ideal, except that its output cannot exceed
±12 V at a current of±10 mA.
(a) Find the minimum load resistor that can be
added between terminal 3 and ground.
(b) Determine the largest allowable magnitude
forviwhen using the minimum load resis-
tance.
5.2.10An op amp has an open-loop frequency response
as shown in Figure 5.2.4.
(a) Find the approximate bandwidth of the circuit
using this op amp:
(i) With a closed-loop voltage gain of 100;
(ii) With a voltage gain of 1000.
(b) Determine the gain–bandwidth product for
this op amp.
5.2.11Consider the generalized circuit shown in Fig-
ure P5.2.11, which contains two elements with
impedancesZ ̄ 1 andZ ̄F. Using the phasor tech-
niques to study the response of op-amp circuits to

sinusoidal signals, obtain a general expression for

A ̄′=V ̄o/V ̄iin terms of the op-amp parameters

A, R ̄ i, andRoand the impedancesZ ̄ 1 andZ ̄F.In

the limit, asRi→∞,Ro→0, andA→∞,

what is the effect on the result? Considering the

high-frequency response, without the assumption

ofA→∞, find an expression forA ̄′.

5.3.1Figure P5.3.1 gives the frequency-response graphs

for a 709 op amp. Choose compensating compo-

nents for the circuit (see Figure 5.3.8) to have a

gain of 100 and a frequency response of up to 100

kHz.

5.3.2Find the maximum amplitude of an output voltage

sine wave that an op amp with a slew rate of 0.5

V/μs can deliver atf=100 kHz.

*5.3.3An op amp has a slew rate of 0.7 V/μs. Find the

maximum amplitude of an undistorted output sine

wave that the op amp can produce at a frequency of

50 kHZ. Also determine the maximum frequency

of undistorted output that the op amp will produce

at an amplitude of 3 V.

−

+

+

Vo

+

− −

−

Vi

ZF

Z 1

−

−

− Figure P5.2.11

80

60

40

20

0

− 20

100 1 k 10 k

Frequency, Hz

Closed-loop voltage gain, dB

100 k 1 M 10 M

C 1 = 5000 pF, R 1 = 1.5 kΩ, C 2 = 200 pF

C 1 = 500 pF, R 1 = 1.5 kΩ, C 2 = 20 pF

C 1 = 100 pF, R 1 = 1.5 kΩ, C 2 = 3 pF

C 1 = 10 pF, R 1 = 0, C 2 = 3 pF

VS = ±15 V

TA = 25 ° C

Figure P5.3.1Frequency response

for various parameters (709).Source:

Fairchild.