TABLE A lists parameters for two different operational amplifiers, A and B.
1. a) Contrast the relative performance of each op-amp in terms of these parameters and state how they compare to that of the ideal op-amp.
b) TABLE B gives two descriptions of operational amplifiers. State, with justifications, which description most closely matches the op-amps of TABLE A.
c) State, with reasons, which op-amp in TABLE A would be most suitable for the applications listed in TABLE C.
d) TABLE D shows the internal circuitry of two op-amps. Identify, with justification, which op-amp circuit is most likely to belong to which op-amp in TABLE A.
2. The amplifier of FIGURE 1 has a closed loop gain of 20 dB and R1 = 10 kΩ. The resistors have a tolerance of 5%.
a. Estimate the output offset voltage of the circuit of FIGURE 1 when the op-amp used is
i) op-amp A of TABLE A
ii) op-amp B of TABLE A.
b. If the circuit of FIGURE 1 uses op-amp A of TABLE A, show how the output offset voltage can be reduced by a circuit modification, calculating the value of any components used.
c. Explain why the technique used in (b) above is relatively ineffectual if op-amp B of TABLE A is used.
Figure 1
3. a) Explain what is meant by ‘unconditional stability' in an op-amp.
b) FIGURE 2 gives the open-loop response of an uncompensated op- amp. Compensation is to be applied to the amplifier to make it unconditionally stable. Estimate the frequency at which the breakpoint of the compensated response must occur.
Figure 2
4. FIGURE 3(a) shows the Bode plot of op-amp THS4021. The manufacturer describes this device as a ‘decompensated op-amp', by which is meant that the frequency compensation is partial as opposed to ‘uncompensated' where no compensation is used at all. The advantages of ‘decompensation' over ‘full compensation' include a higher open-loop gain and better slew rate. Greater care, however, is need in the use of such an op-amp as frequency stability cannot be assured.
a) Estimate the phase margin and unity gain BW of the THS 4021.
b) FIGURE 3(b) shows the THS4021 in a practical op-amp circuit with applied external compensation. Determine an expression for the low frequency gain of the circuit.
Figure 3(a)
Figure 3(b)
5. In FIGURE 4(a) the input voltage Vin is swept from 0 to 5 V. The supply voltage is a single-rail 5 V. Explain the shapes of the output responses of the two op-amps shown in FIGURE 4(b).
[TABLE E gives some further information on these op-amps.]
6. Estimate the maximum frequency of a sinusoidal input signal of 10 mV peak, for distortion-free output, when applied to an op-amp circuit of closed-loop gain of 100, if the op-amp used is the:
Figure 4
a) TL072
b) TLV2362.
[TABLE E gives some further information on these op-amps.]
Attachment:- tables.rar