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ee 345 lab 11 mosfets fall 93

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ee 345 lab 11 mosfets fall 93

    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

    and units.

    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

114

     21311141

    312

    411132

    12106351084

    6 9

    87579

     Figure 11.1. CD4007 MOS Array

    +10 V+10 V

    DVM1414

    4

    43

    35

    5DVM77

     +15 V

    14;10 k

    ;10 M-+

    +0.1F4vo_A-+3M1

    0.1F57

Figure 11.2. Measuring Figure 11.3. Illustrating the Figure 11.4. Resistor as Drain

     Threshold Voltage Body Effect

    Load Element

    EE 345 LAB # 11 - MOSFET CIRCUITS PAGE 2

    +15 V

    +15 V

    11141214

    M36M2M210

    12139;10 M-+;10 M-+

    ++0.1Fv0.1F4v4o10o__A-+A-+M43M13M1

    0.1F0.1F59577

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.

     Questions:

     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

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