Lab 23 TF EIM

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Inverting OP Amp

1. Construct the inverting amplifier according to the wiring diagram below.

TF EIM Lab23.png

Here is the data sheet for the 741 Op Amp

File:LM741CN OpAmp.pdf


Use R1=1kΩ and R2=10kΩ as starting values.

2. Insert a 0.01 μF capacitor between ground and both Op Amp power supply input pins. The Power supply connections for the Op amp are not shown in the above circuit diagram, check the data sheet.

Gain measurements

1.) Measure the gain as a function of frequency between 100 Hz and 2 MHz for three values of R2 = 10 kΩ, 100 kΩ, 1MΩ. Keep R1 at 1kΩ.

2.)Graph the above measurements with the Gain in units of decibels (dB) and with a logarithmic scale for the frequency axis.

Impedance

Input Impedance

  1. Measure Rin for the 10 fold and 100 fold amplifier at ~100 Hz and 10 kHz frequency.

Output Impedance

  1. Measure Rout for the 10 fold and 100 fold amplifier at ~100 Hz and 10 kHz frequency. Be sure to keep the output (Vout) undistorted

Vio and IB

Vout=R2R1V1+(1+R2R1)Vio+R2IB

Use the above equation and two measurements of Vout, R1, and R2 to extract Vio and IB.

  1. measure Vout for R1 = 1 kΩ, R2 = 100 kΩ, andVin=0 (grounded).
  2. measure Vout for R1 = 10 kΩ, R2 = 1 MΩ, andVin=0 (grounded).
  3. You can now construct 2 equations with 2 unknowns Vio and IB.

Iio

Now we will put in a pull up resistor R3=R1R2R1+R2 as shown below.

TF EIM Lab23a.png

Instead of the current IB we have the current Iio

Vout=R2R1V1+(1+R2R1)Vio+R2Iio

Use the same technique and resistors from the previous section to construct 2 equations and 2 unknowns and extract Iio, keep Vin=0.

The offset Null Circuit

TF EIM Lab23 b.png

  1. Construct the offset null circuit above.
  2. Adjust the potentiometer to minimize Vout with Vin=0.
  3. Use a scope to measure the output noise.

Capacitors

Revert back to the pull up resistor

Capacitor in parallel with R2

TF EIM Lab23 c.png

  1. Select a capacitor such that1ωC2R2 when ω= 10 kHz.
  2. Add the capacitor in parallel to R2 so you have the circuit shown above.
  3. Use a pulse generator to input a sinusoidal voltage Vin
  4. Measure the Gain as a function of the Vin frequency and plot it.

Capacitor in series with R_1

TF EIM Lab23 d.png

  1. Select a capacitor such that1ωC2R1 when ω= 1 kHz.
  2. Add the capacitor in series to R1 so you have the circuit shown above.
  3. Use a pulse generator to input a sinusoidal voltage Vin
  4. Measure the Gain as a function of the Vin frequency and plot it.

Slew rate

Measure the slew and compare it to the factory spec.

Power Supply Rejection Ratio

  1. Set V_{in} = 0.
  2. Measure Vout while changing Vcc

Output voltage RMS noise ΔVRMSout

Measure the RMS noise in Vout when Vin = 0 .

Forest_Electronic_Instrumentation_and_Measurement