Transcript Design of an Instrumentation Amplifier Instrumentation Amplifier Bias Voltage Generation Differential Pair with Active Load.

Design of an
Instrumentation Amplifier
Instrumentation Amplifier
Bias Voltage Generation
Differential Pair with Active Load
Anatomy of a Different Pair with
Active Load
Differential Pair
with Active Load
(Sec. 10.3)
Differential Pair
(Sec. 10.3)
Current Mirror
(Section 9.2)
Bias Voltage Generation
Schedule
Cascode (Section 9.1, 11/14)
Current Mirror (Section 9.2.3, 11/19)
Bias Circuitry (Handout, 11/26)
Differential Pair (Section 10.3, 11/28)
Differential Pair with Active Load
(Section 10.6, 12/3)
• Instrumentation Amplifier (12/5)
•
•
•
•
•
Common Source Amplifier
Design
Design spec:
1 uA of bias current
AV=-30 V/V of gain.
Measure Peak to Peak Voltage
The gain is approximately 30.
Voltage Gain
Design Exploration
• Initial results
– ro1=2.228 Mohms
– ro2=5.32 Mohms
– Av=-31.4 V/V
– gmovergds1=44.57
– gmvoergds2=42.5
Design: If we can increase ro1, we can potentially raise the gain!
Cascode Circuit
Matlab Computation
ro2 is 1.526 Mohms
gmovergds_2=30 Mohms
Rout is 55.2 Mohms
Gain Calculation
We should be increase the gain from 30 to 97.
DC of Vout is too low!
The gate bias voltage
for T0=284.4 mV
The gate bias voltage
For T1 is 0.33 V +0.3 V
0.63 V
The output voltage does
Is only 71.87 mV
What happens?
Calculate the Gain of a Circuit
Using Norton Equivalent Circuit
Short Circuit Transconductrance
Sweep DC Voltage
Copy from Cellview
Define DC voltage as a variable.
Setup the Sweep
Run Parametric Analysis
Use Sweep to Zoom on the
Correct Gate Bias Voltage
We want to keep the output voltage close to 0.6 V.
Adjust Gate Voltage
Gate voltage of T0:
255 mV
Matlab: 284 mV
We were off by 31 mV
Vin and Vout
A gain of 88!
A faster way to calculate voltage gain is using the calculator.
Using the Calculator
Calculate Peak to Peak Voltage