EE559 – Integrated Analog Electronic Circuits

Mini Project

Electronics laboratory

OBJECTIVE:

- To become familiarize with designing a long tail pair for given parameters.
- To implement the hardware setup for long tail pair.
- To observe the characteristics of the implemented long tail pair.

-Maximum undistorted output swing.

-DC voltage gain.

-Common mode rejection ratio.

-3dB bandwidth.

APPARATUS:

- SSM2212 SMD dual transistors (2 ICs)
- 680 Ohm 1206 SMD resistors
- 1.8 kOhm 1206 SMD resistors
- 6.8 kOhm 1206 SMD resistors

CIRCUIT DIAGRAM:

*Figure1. Schematic diagram of the long tail pair*

THEORY:

Using KVL ……….. (1)

Using KCL ……….. (2)

Trans-conductance ……….. (3)

DC Voltage gain ……….. (4)

Maximum Undistorted

Output swing ……….. (5)

*Figure 2. Relevant Graphs and Equations*

PROCEDURE:

- Select and calculate Vdc1, Vdc2, Rref and Rc values for the given specifications.

- DC voltage gain (A
_{V}) : 10 ( 20log(A_{V}) = 20 dB ) - Maximum undistorted output swing : 1V

- Simulate above circuit using QUCS software and observe following parameters.

- Maximum undistorted output swing.
- DC voltage gain
- Input and output waveforms for 200 Hz
- Differential gain for 0 to 100MHz
- Common mode gain for 0 to 100MHz
- CMRR for 0 to 100MHz
- 3dB bandwidth

- Use a PCB layout designing software (eg. PROTEUS) to design the PCB layout.

**(Note: You should show this design to instructor before implementing hardware) **

- Using selected resistor values and transistor ICs implement the hardware.
- Take following observations to verify the operation of the long tail pair.
- Observe output differential voltage by applying -200mV to 200mv input differential DC voltage in the steps of 10mV and plot input differential voltage vs. output differential voltage in order to observe maximum undistorted output voltage swing.
- From the above graph identify DC voltage gain.
- Apply 10mV differential DC input voltage and observe the amplification.
- Apply 200Hz 10mV sinusoidal differential input and observe the output differential waveform.
- For differential mode change the frequency of the input differential sinusoidal and observe output waveform for 0, 10Hz, 100Hz, 1 kHz, 10 kHz, 100 kHz, 1 MHz, 10 MHz, and 100 MHz and plot frequency (dB) vs. Differential mode gain plot.
- For common mode change the frequency and observe output waveform for 0, 10Hz, 100Hz, 1 kHz, 10 kHz, 100 kHz, 1 MHz, 10 MHz, and 100 MHz and plot frequency (dB) vs. Common mode gain plot.
- Using above values obtain the frequency (dB) vs. CMRR plot.
- Using the results obtain the 3dB bandwidth of the differential amplifier.

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