Analog Circuit Design Laboratory Report - MyWeb at WIT ...

input stage VO’ was calculated to be 35mV. The differential gain of the output stage was
equal to 1, so the overall circuit was equal to ADIFF and VO was calculated to be 35mV.
VO was measured to be 34.9mV. E1 and E2 were measured as 458.9mV and
447.7mV, respectively. Using Equation 15 ADIFF was equal to 3.12. Both VO and ADIFF
were within 4% of the calculated values.
Resistor aR was then changed to a 100-kΩ resistor to increase the instrumentation
amplifiers differential gain. Using Equation 14, a, equals 5, VO’ equals 16.4 mV, and VO
equals 16.4 mV. Using the DMM, VO’ was measured as 15.75 mV, and VO was
measured as 17.0 mV. The DMM was then used to measure E1 and E2. Their values
were 458.9 mV and 447.7 mV, respectively. Using Equation 15 ADIFF was calculated to
be 1.52. Both VO and ADIFF were within 10% of the calculated values.
The differential gain for this circuit could be adjusted to any value by changing
aR. The actual resistor value was determined using Equation 14 and Equation 15. To
achieve an overall circuit gain of 100, aR must be equal to 404-Ω.
Adding a Voltage to the Reference Terminal:
The reference terminal of the instrumentation amplifier was modified to provide an offset
voltage. This was done by constructing the circuit shown in Figure 35. This circuit was
then connected to the reference terminal of the circuit shown in Figure 35. The
connection between the reference terminal and ground was removed.
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