DESIGN Project #2 Solution



Design a single stage FET amplifier to the following specifications. This is an individual effort; similar designs will not get the extra credit.


Transistor: NMOS FET type V2N2222, Kn = 0.06 A/V2, VTN = +2.6V, r0 = large.

Resistor-only DC biasing (no DC current sources allowed)

Single DC voltage supply, VDD = +30.0 V

All resistors <= 500kΩ

All coupling and bypass capacitors = 1 (large = 1 Farad)

Load Resistor, RL = last 4 digits of your student N#, if RL < 500, then RL = RL + 500

Target small signal voltage gain (magnitude) is based on your load resistance and is


RL (ohms) Gain, |AV|

500-2,000 2

2,001-8,000 5

8001-10,000 10

Maximum DC power supply current: IDD < 100mA

Maximum DC power dissipation for transistor: PD < 500mWatt

Assume that the transistor small signal ro = infinite

Extra Points for a design with low power dissipation, PD.

Extra Points if your design is stable with changes in temperature.

1. HAND CALCULATIONS: Design a single stage NMOS FET amplifier to achieve the above specifications. As this is an amplifier circuit, you should design for a FET in saturation mode.

a. This is a design project; show all steps for selection of resistors and bias point. Submit all hand calculations for voltage gain, input resistance and output resistance. Show that your transistor is saturated. Extra points for neatness.

b. What is your load resistance, RL?

c. Submit your complete schematic and label all resistor values.

d. On a table, list the following calculated parameters i. Voltage Gain, Av?

ii. Input Resistance, Rin?

iii. Output Resistance Rout? (not including RL)

e. Calculate the amplitude of the input source, vin, to have the transistor just operating at the condition for small signal. What is this amplitude for vin?

f. Extra Points: Discuss how your design was optimized for low power


2. PSPICE: Simulate your design using an input sinusoid, vin, operating at 1kHz with a peak amplitude equal to 1mV. If using Orcad, use the PSpice model for the VN2222 found in theEVALAA” library.

a. Simulate the DC performance of your design. Submit your PSpice schematic showing values for DC voltage and DC current on the schematic. Your schematic should clearly show the resistor values and DC voltages/currents.

b. What are the simulated DC bias parameters? Submit a table showing the simulated values for IDD, ID, VGS, VDS, and PD=(VDS)(ID)? Is your power supply current, IDD < 100mA? Is your transistor power rating < 500mW?

c. Simulated Gain: Simulate a Transient analysis, submit a plot showing vin and vout versus time under small signal conditions. The time scale is 0 to 3 msec, adjust themax. time step” for a smooth sinusoidal curve (0.02msec). Ideally, plot both curves on the same graph but separate graphs are also acceptable. Are your waveforms inphase or outofphase? Is there any distortion in the output sinusoidal waveform, vout? What is the simulated


voltage gain,

Av =



? Use cursors to measure the peak amplitudes of

each voltage waveform and calculate the small signal gain by taking the ratio.

Compare the simulated value to your calculated value, what is the percent

difference between the two𝑠𝑠𝑠�𝑠𝑠𝑠�𝑠𝑠𝑠𝑠𝑠𝑠𝑠�𝑠�𝑐𝑐𝑠𝑠𝑠�𝑐𝑐𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠�𝑠𝑠 𝑥𝑥100%?


d. Simulated Input Resistance: Place voltage and current probes on the left side of the input capacitor. Simulate a Transient analysis, submit a plot of vin and iin versus time under small signal conditions, these waveforms should be


on two separate plots. What is the simulated input resistance,

Rin =

in ?


Use cursors to measure the peak amplitudes of each waveform and calculate the ratio. Compare the simulated value to your calculated value.

e. Simulated Output Resistance: Remove the input voltage source. Place a short across the input. Remove the load resistor, RL. Please a voltage source at the output. Simulate a Transient analysis. Submit a plot of vout and iout versus time under small signal conditions. What is the simulated input


Rout =



? Use cursors to measure the peak amplitudes of

each waveform and calculate the ratio. Compare the simulated value to your calculated value.

f. Extra Points: Simulated Gain Over Temperature: Simulate the transient output voltage over temperature. You will need to return the input voltage source and the load resistance back into the circuit and remove the output voltage source. Using Orcad, in the simulation analysis profile, there is a temperature sweep setting. Add this checkbox to the transient simulation. Enter the following three temperatures: 40C, +25C and +85C. Run the transient simulation. The three temperature plots will be superimposed onto the same graph. Submit the plot showing the output voltage with changing temperature. Calculate the gain at each temperature knowing the input voltage is 1mV. Is your gain stable over temperature? Submit a table of the percentage change in gain over temperature and use the gain at +25C as the reference.