Lab 23 TF EIM

Inverting OP Amp

1. Construct the inverting amplifier according to the wiring diagram below.
2. insert a 0.1 [math]\displaystyle{ \mu }[/math]F capacitor between ground and the OP power supply input pin.

Gain measurements

1. Measure the gain as a function of frequency between 100 Hz and 2 MHz for three values of R_2 = 10 k[math]\displaystyle{ \Omega }[/math], 100 k[math]\displaystyle{ \Omega }[/math], 1M[math]\displaystyle{ \Omega }[/math].
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 [math]\displaystyle{ R_{in} }[/math] for the 10 fold and 100 fold amplifier at ~100 Hz and 10 kHz frequency.

Output Impedance

1. Measure [math]\displaystyle{ R_{out} }[/math] for the 10 fold and 100 fold amplifier at ~100 Hz and 10 kHz frequency. Be sure to keep the output ([math]\displaystyle{ V_{out} }[/math]) undistorted

[math]\displaystyle{ V_{io} }[/math] and [math]\displaystyle{ I_{B} }[/math]

[math]\displaystyle{ V_{out}= -\frac{R_1}{R_2} V_1 + \left ( 1 + \frac{R_1}{R_2}\right)V_{io} + R_2 I_B }[/math]

Use the above equation and two measurements of [math]\displaystyle{ V_{out} }[/math], [math]\displaystyle{ R_1 }[/math], and [math]\displaystyle{ R_2 }[/math] to extract [math]\displaystyle{ V_{io} }[/math] and [math]\displaystyle{ I_B }[/math].

1. measure [math]\displaystyle{ V_{out} }[/math] for [math]\displaystyle{ R_1 }[/math] = 1 k[math]\displaystyle{ \Omega }[/math], [math]\displaystyle{ R_2 }[/math] = 100 k[math]\displaystyle{ \Omega }[/math], and[math]\displaystyle{ V_{in} }[/math]=0 (grounded).
2. measure [math]\displaystyle{ V_{out} }[/math] for [math]\displaystyle{ R_1 }[/math] = 10 k[math]\displaystyle{ \Omega }[/math], [math]\displaystyle{ R_2 }[/math] = 1 M[math]\displaystyle{ \Omega }[/math], and[math]\displaystyle{ V_{in} }[/math]=0 (grounded).
3. You can now construct 2 equations with 2 unknowns [math]\displaystyle{ V_{out} }[/math] and [math]\displaystyle{ I_B }[/math].

[math]\displaystyle{ I_{io} }[/math]

Now we will put in a pull up resistor R_3 as shown below.

Instead of the current [math]\displaystyle{ I_B }[/math] we have the current [math]\displaystyle{ I_{io} }[/math]

[math]\displaystyle{ V_{out}= -\frac{R_1}{R_2} V_1 + \left ( 1 + \frac{R_1}{R_2}\right)V_{io} + R_2 I_{io} }[/math]

Use the same technique and resistors from the previous section to construct 2 equations and 2 unknowns and extract [math]\displaystyle{ I_{io} }[/math], keep [math]\displaystyle{ V_{in} }[/math]=0.

The offset Null Circuit

1. Construct the offset null circuit below.
2. Adjust the potentiometer to minimize [math]\displaystyle{ V_{out} }[/math] with [math]\displaystyle{ V_{in}=0 }[/math].
3. Use a scope to measure the output noise.

Capacitors

Revert back to the pull up resistor

Capacitor in parallel with [math]\displaystyle{ R_2 }[/math]

1. Select a capacitor such that[math]\displaystyle{ \frac{1}{\omega C_2} \approx R_2 }[/math] when [math]\displaystyle{ \omega }[/math]= 10 kHz.
2. Add the capacitor in parallel to [math]\displaystyle{ R_2 }[/math] so you have the circuit shown below.
3. Use a pulse generator to input a sinusoidal voltage [math]\displaystyle{ V_{in} }[/math]
4. Measure the Gain as a function of the [math]\displaystyle{ V_{in} }[/math] frequency and plot it.

Capacitor in series with R_1

1. Select a capacitor such that[math]\displaystyle{ \frac{1}{\omega C_2} \approx R_1 }[/math] when [math]\displaystyle{ \omega }[/math]= 1 kHz.
2. Add the capacitor in series to [math]\displaystyle{ R_1 }[/math] so you have the circuit shown below.
3. Use a pulse generator to input a sinusoidal voltage [math]\displaystyle{ V_{in} }[/math]
4. Measure the Gain as a function of the [math]\displaystyle{ V_{in} }[/math] 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 [math]\displaystyle{ V_{out} }[/math] while changing [math]\displaystyle{ V_{cc} }[/math]

Output voltage RMS noise [math]\displaystyle{ \Delta V_{out}^{RMS} }[/math]

Forest_Electronic_Instrumentation_and_Measurement