Lab 3

ENSC 220 – Lab 3 Report

Review of Function-Generator / Oscilloscope Operation & Op-Amp Circuits

Names / IDs / Bench

• Kian Bellinger – 301554307
• Tyler Lee – 301560642
• Kavahn Ahluwalia – 301581033
• Bench 2

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Part 1 - Instrumentation

• I feel like we don’t need to make a report for part 1 as there is not calculations or anything other than following the steps

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Part 2 – Op-Amp Circuits

3.1 Component Inventory (measured with DMM)

Nominal	Measured (kΩ)
2 k2	2.177
3 k3	3.240
10 k	9.867

All circuits powered from ±12 V (DMM: +12.015 V / –12.012 V).

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3.2 Comparator #1

Circuit – Voltage divider sets a fixed reference for the non-inverting input; inverting input receives a 100 Hz 1 Vpp triangle

3.2.1 Reference voltage calculation

The divider uses the 10 kΩ (top) and 3 k3 Ω (bottom) resistors from +12 V to ground:

$$V_{REF,calc}=V_{CC}\frac{R_{bot}}{R_{top}+R_{bot}}=12.015\text{V}\times \frac{3.240}{9.867+3.240}=2.97\text{V}$$

3.2.2 Measured values

Parameter	Value
$(V_{REF,DMM})$	3.044 V
$(V_{REF,scope})$	3.20 V
$Op-amp(V_{O(max)})$	+11.60 V
$Op-amp(V_{O(min)})$	–10.80 V

Figure x – Triangle input (yellow) & comparator output (blue) with cursor on $(V_{REF})$.

Discussion – The measured reference is within ≈ 2 % of theory; the offset between +11.60/–10.80 V and ideal rails indicates the TL072’s output-swing limit when driving 5 kΩ scope load.

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3.3 Comparator #2

Comparator #2 swaps the divider to the inverting input, producing an inverted logic polarity.

Parameter	Value
Same $(V_{RE{F}_{calc}})$	2.97 V
$(V_{RE{F}_{scope}})$	3.20 V
$(V_{O(max)})/(V_{O(min)})$	unchanged

Figure 5 – Comparator #2 waveforms.

Observation – Output toggles when the input falls through ($V_{REF})$, confirming inversion.

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3.4 Inverting Amplifier

Schematic parameters $–(R_{in}=3.240k\Omega ),(R_f=9.867k\Omega ),(f_{in}=500\text{Hz}),(V_{in}=1\text{Vpp})$.

3.4.1 Gain theory

$$A_{v,calc}=-\frac{R_f}{R_{in}}=-\frac{9.867}{3.240}=-3.045$$

3.4.2 Measurements

Quantity	Value
$(V_{i{n}_{pp}})$	2.07 V
$(V_{ou{t}_{pp}})$	6.06 V
$(A_{v_{scope}})$	$(-)2.94V$

Figure 6 – Inverting amp; note phase inversion (blue vs yellow).

% error
$\%\text{error}=\left|\frac{A_{scope}-A_{calc}}{A_{calc}}\right|\times 100\%=\frac{|-2.94+3.045|}{3.045}\times 100\%=3.4\%$

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3.5 Non-Inverting Amplifier

Schematic parameters$–(R_1=3.240k\Omega )\text{ to ground },(R_f=9.867k\Omega )$ feedback.

3.5.1 Gain theory

$$A_{v,calc}=1+\frac{R_f}{R_1}=1+\frac{9.867}{3.240}=4.045$$

3.5.2 Measurements

Quantity	Value
(V_{in(pp)})	2.09 V
(V_{out(pp)})	8.07 V
(A_{v,;scope})	3.86

Figure 7 – Non-inverting amplifier waveform; no phase inversion.

% error
$\%\text{error}=\frac{|3.86-4.045|}{4.045}\times 100\%=4.6\%$