LABORATORY EXERCISE 8 - MOSFET CIRCUITS
Objective: to study the characteristics of, measure the parameters of, and construct typical basic circuits with CMOS transistors.
Components: 1 CD4007 MOS Array, 2 0.1-；F capacitors, and resistors as follows: 1-
10M;, 2-10k;, and 1-1k;.
Determine the Characteristics:
1. Place your chip on your breadboard.
2. Connect the substrate (pin 7) to the source of the (3,4,5)-pin n-channel MOSFET (pin 5). (See Figure 12.1.)
3. Place wires in holes that are electrically connected to pins 3 (the gate), 4, (the drain), and 5, (the source). The other ends of these wires should not be connected to anything, i.e., they should be extending up into the air.
4. Take you breadboard to the curve tracer. Connect the gate (pin 3) to the base terminal of the curve tracer; the drain (pin 5) to the collector; and the source (pin 5) to the emitter. Make sure the substrate (pin 7) is still connected to the source (pin 5).
5. Get your TA to show you what dial settings you use to get the characteristics of a MOSFET.
6. Carefully sketch what you see on the screen in your notebook. The horizontal axis
; the vertical, i. Label your axes and steps with variable, numeric values, will be vDSD
Determine the Parameters:
7. Construct the circuit shown in Figure 11.2.
8. Read the DVM and record the value, V. Calculate the threshold voltage, V, DVMt
from V = V - V. tDDDVM
9. Shunt the DVM with a 1-k; resistor. Record the DVM reading and calculate the
drain current, I, from I = V / R. DDDVM
10. Calculate the drain voltage, V, from V = V - V. DDDDDVM
11. Notice that the drain voltage is the same as the gate voltage; and since the source is gounded, this is also the gate to source voltage, V. GS212. Calculate the conductivity parameter, K, from I = K (V - V). DGSt
13. In order to evaluate the importance of the substrate connections, measure the threshold voltage without the source connected to the substrate by doing the following: Connect pin 4 to V. Connect the DVM between pin 5 and ground. (See Figure DD
11.3.) Read the DVM and compare to the value of V obtained in step 8 where the t
lowest voltage terminal IS connected to the substrate.
EE 345 LAB # 11 - MOSFET CIRCUITS PAGE 1
Figure 11.1. CD4007 MOS Array
+10 V+10 V
Figure 11.2. Measuring Figure 11.3. Illustrating the Figure 11.4. Resistor as Drain
Threshold Voltage Body Effect
EE 345 LAB # 11 - MOSFET CIRCUITS PAGE 2
12139;10 M-+;10 M-+
Figure 11.5. Transistor as Drain Figure 11.6. Current Mirror (Active Load) as Drain
Load Element Load Element
EE 345 LAB # 11 - MOSFET CIRCUITS PAGE 3
A Discrete Common-Source Amplifier: Resistor for the Drain Load Element
14. Construct the circuit shown in Figure 11.4.
15. Measure V and calculate I from I = (V - V)/R. DDDDDD2. (Note that V = V for this circuit. 16. Calculate I from I = K(V-V)DGSDDGSt
Compare with the result from step 15.
17. Inject a 1-kHZ, 0.2-Vpp sine wave into node A. (If you cannot get a 0.2-Vpp sine wave from your function generator, use a 2-Vpp sine wave and a 10k;-1k; voltage
divider.) Record the open circuit output voltage, v. o
18. Put a 10-k; load resistor from v to ground and measure the output voltage across o
the load resistor.
19. Reduce the input signal to 0.1 Vpp and measure the open circuit voltage and the output voltage across the load resistor again.
20. Calculate the voltage gain, v/v, in all four cases and arrange your results in a table. oi
21. Using the parameters, calculate the theoretical voltage gain and theoretical open circuit voltage gain.
Enhancement Loaded Amplifier: Enhancement NMOS Transistor for the Drain Load Element
22. Construct the circuit shown in Figure 11.5.
23. With no input signal measure the voltage V. D
24. Calculate the drain current as was done in Step 16 above.
25. Repeat steps 17 thru 21 for this configuration.
CMOS Active Loaded Amplifier: Constant Current Source for the Drain Load Element
26. Construct the circuit shown in Figure 11.6.
27. With no input signal measure the voltage V. D
28. Calculate the drain current as was done in Step 16 above.
29. Repeat steps 17 thru 21 for this configuration.
1. Using the tables created in steps 20, 25, and 29 above, discuss the stability with respect to changes in signal level of the circuits with the three different types of load elements.
2. Using the tables created in steps 20, 25, and 29 above, discuss the stability with respect to the amplifier load of the circuits with the three different types of load elements.
Suggested Additional Measurements: [To be done for credit after ALL the regular
measurements are complete and ALL questions answered.]
Determine the input and output resistance of your amplifier circuit: For one or more of your amplifiers:
* Connect a 10-k; resistor in series with the amplifier. Record the signal voltage and the voltage across this series resistor. Use the voltage divider rule to determine the input resistance.
* Connect two 10-k; resistors in series as the amplifier load. Record the voltage of the nodes on both sides of the resistor closest to the amplifier. Use the voltage divider rule to determine the output resistance.
[Extra credit: 1 amplifier, 20% ; 2 amplifiers, 35% ; or 3 amplifiers, 45% .] EE 345 LAB # 11 - MOSFET CIRCUITS PAGE 4
EE 345 LAB # 11 - MOSFET CIRCUITS PAGE 5