ECE 2212

EXPERIMENT 5

24 October 2013

MOSFET I-V Characteristics and MOSFET Circuits

PURPOSE

To measure the I-V characteristics of an N-channel MOSFET and a P-channel MOSFET on the CD 4007 array.

PRELAB

Prepare a detailed circuit diagram in your notebook of how you will connect an NMOS and PMOS for measuring the I-V curves. Study the material in Chapter 4. A complete manufacturer’s data sheet has been posted on the class WEB page.

The device you will use throughout this experiment is a CD4007B Transistor array. It contains three N-channel and three P-channel devices. Detailed schematic diagrams and pinouts are available on the data sheet and also give below. Please use care when working with these chips. They are very susceptible to excessive voltage and ESD (Electro-Static Damage). Do not exceed the experiment settings in an attempt to make your experiment work. The pin configuration is given in Figure 5.1. Note that you will be using the CD4007B which have a lower maximum voltage rating than the CD4007UB. The diagrams are the same for both the “B” and “UB” suffix devices. Avoid exposing the chip to ESD (electrostatic damage). This time of the year often has low relative humidities which make ESD more of an issue. Do not exceed the V_DD maximums!!!

Study the I-V curves provided in the data sheets so that you have some idea of what to expect. Also study the chip circuit diagram. You should be able to identify the operation and function of all of the individual devices.

Figure 5.1 Pin Configuration of CD4007.

Warning: Pin 14 should always be connected to the most positive dc voltage in the circuit. Pin 7 will always be connected to the most negative dc voltage in the circuit

(or else )!!!

PROCEDURE

I-V Characteristic of an N-channel MOSFET

Ø Connect the circuit shown in Figure 5.2. Use the NMOS connected to pins 6, 7, and 8 and 14. Remember to connect pin 14 also to the +VDS supply. Pin 7 is shown connected to ground. Use the built-in mA meter on the power supply to measure I_D. Use the voltage readout on the power supply as you sweep V_DD from 0 to 10 volts for each value of VGS from 0 to 6 volts in 1-volt increments. Note that V_T is in the 1 to 2 volt range. Refer to the data sheets.

Figure 5.2 I_D-V_DS As A Function of V_GS Characteristic Measurement For an NMOS

Ø Note that you should keep below I_D = 10mA; since this is the maximum rated value for this chip, consequently you may not be able to use all values of V_GS depending upon your chip. Plot data as you proceed.

Ø Plot your data and use a linear regression (least squares fit) to extract values for VTO, LAMBDA, and KP and develop a SPICE model that compares well with your measured curves. The objective is to obtain I_D versus V_DS for several different values of V_GS. Look at Figures 5 and 8 on the CD 4007 data sheet as a guide as to what to expect. You will have to assume W/L=1 because you do not know the actual values of W and L and then adjust KP accordingly. This model development from your parameter extractions should be included in your report. Develop a Shichman-Hodges model equation for your NMOS.

I-V Characteristic of a P-channel MOSFET

Ø Connect the circuit shown in Figure 5.3. Use the PMOS connected to pins 6, 13 and 7, and 14. Use the built-in mA meter on the power supply to measure I_D. Use the voltage readout on the power supply as you sweep V_DD = -V_DS from 0 to 10 volts for each value of VGS from 0 to -6 volts in 1-volt increments. Note that V_T is in the -1 to -2 volt range. Refer to the data sheets.

Figure 5.3 I_D-V_DS As A Function of V_GS Characteristic Measurement For an PMOS

Ø Use the PMOS connected to Pins 6, 13 and 7, and 14. Note that Pin 13 is the PMOS drain.

Ø Note that you should keep below |I_D| = 10mA; since this is the maximum rated value for this chip, consequently you may not be able to use all values of V_GS depending upon your chip. Plot data as you proceed.

Ø Plot your data and use a linear regression (least squares fit) to extract values for VTO, LAMBDA, and KP and develop a SPICE model that compares well with your measured curves. The objective is to obtain I_D versus V_DS for several different values of V_GS. Look at Figures 9 and 10 on the CD 4007 data sheet as a guide as to what to expect. You will have to assume W/L=1 because you do not know the actual values of W and L and then adjust KP accordingly. This model development from your parameter extractions should be included in your report. Develop a Shichman-Hodges model equation for your PMOS.

To Assist with your mathematics skills: