Q4: Consider the uA741C-based op-amp amplifier circuit shown below; The input voltage, Vi, is 2.5 volts. R2 is 5,000 ohms and RI is 1,000 ohms : R2 R1 vo

Figure QI shows the circuit diagram of a "Logarithmic Amplifier". In this circuit the feedback resistor of a normal inverting amplifier is replaced by a silicon diode. Since the current flowing through the diode increases exponentially with the voltage across the diode, the voltage across the diode will be proportional to the logarithm current flowing through it. Hence the output of the circuit is proportional to the logarithm of the input voltage. QI DI RIN Al Figure QI The current flowing through a diode is given by the Shock' y Diode Equat n: 1,=1, (e" =1) where , is the current flowing through the diode g is the charge on the electron (given at the back of the examination sheet) V, is the voltage across the diode K, is Boltzmann's constant (given at the back of the examination sheet) Tis room temperature (given at the back of the examination sheet) Given that /,> 1, an approximate expression for V, as a function of I, is Continued overleaf Page 2 of 9 QI (a) 0) Neglecting any input…

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2. 3. 5. Using the data when the gate voltage is 0, explain how you could use your JFET as a two-terminal current source that gives a current of Ipss. (a) Does the experimental data indicate that the transconductance is a constant at all points? (b) From your experimental data, what evidence indicates that a JFET is a nonlinear device? Why should a JFET be operated with only reverse bias on the gate source?