EE 2212

PROBLEM SET 10

 

1.   The following is a circuit diagram of a National Semiconductor LM 741 operational amplifier. Recall from the beginning of the semester that I mentioned that you will be able to analyze key sub-circuits of operational amplifiers and related circuits by the end of the semester.  I have circled key elements of the current source system you are analyze in the LM 741. Assume all |VBE(on)| = 0.7 volts (for both npn and pnp). V+ = 12 volts and V- = -12 volts. All npn transistors have equal junction areas and all pnp transistors have equal junction areas.    741signetics.jpg  You will have to solve a transcendental equation to obtain IC10.

Compute values for IREF, IC10, and I13.

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 2. Text 15.1  BJT Differential Pair 

 

3.  Text 15.4 BJT Differential Pair  Similar to Text 15.1

 

4.   Modified from an old quiz.  Refer to the modified and annotated partial diagram of a Fairchild μA725 operational amplifier integrated circuit.  Assume all npn BJTS are matched with β = 150 and an Early voltage of  VA = 100 volts.  IC3 = 31 μA.     The circuit is connected to ± 12 volt power supplies.  Compute the following quantities for this circuit (Observe, you will have to compute a value for R4):

 

(a)       The differential mode voltage gain, Adm.

(b)       The common-mode current gain, Acm.

(c)        Common-mode rejection ratio, CMRR, numerically and in dB.

 

 

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You may be asked to do this over Summer Break

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