Lab 9 - EE 420L 

Authored by Iain Drews drewsi2@unlv.nevada.edu

4/22/15 

Lab description

In this lab you may need to use two, or more, CD4007 chips from the same production lot (see date code on the top of chip) to ensure using a BMR to bias a current mirror is possible. If the CD4007 chips are not from the same production lot they will not "match" so current mirrors will not be possible.

• note in the above schematic m2 has 2 parallel mosfets

• Build your BMR design and characterize it as you did in the pre-lab
• Measure how the current varies through each current mirror as the voltage across the mirror changes.

• Of course the current in the NMOS (PMOS) current mirror goes to zero as the voltage on the drain of the output device moves towards ground (VDD)

Yellow VDD Purple: Vbias P Blue: Vbias N Note how VbiasP is relative to VDD and VbiasN is relative to GND from this we can determine VDD-VSG=3.32 and VSG=1.40
Yellow VDD Purple: voltage across a 1k ohm resistor for current Blue: Vbias N 152mv/1kohm= 152uA

• Using these current mirrors drive two gate-drain connected transistors
• For the first experiment use the NMOS current mirror to drive two PMOS gate-drain connected devices. 
• Use the voltages on the gate-drain connection of the two devices to bias a cascode current mirror (characterize this mirror as before)

Yellow VDD Purple: Vcascodep (VG on the first cascode mosfet) Blue: Vbias N note how the voltages mirror VDD when they reach threshold
Yellow VDD Purple: voltage across a 1k ohm resistor for current Blue: Vbias N 218mv/1kohm= 218uA

• For the second experiment switch, that is, use the PMOS current mirror to drive two NMOS gate-drain connected devices.
• Again, use these two voltages to bias an NMOS cascode current mirror then characterize.

Yellow VDD Purple: VDD-Vdsat Blue: VCascoden (VG on the first cascode mosfet) Note how the voltages flatten out and stop mirroring vdd when they reach threshold
Yellow VDD Purple: voltage across a 1k ohm resistor for current Blue: VCascoden 176mv/1kohm= 176uA

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