Two-Stage RC Coupled BJT Amplifier Implementation and Gain Measurement

The first step in implementing the two-stage RC coupled BJT amplifier is to collect all the necessary components. This involves gathering various resistors, capacitors, and two NPN BJTs (in this case, BC547). Proper identification of components based on their specifications is crucial for successful assembly.

Once the components are collected, the next step is to carefully assemble the circuit on a breadboard, following the circuit diagram outlined in the experiment. It’s important to ensure that every connection is secure and correctly oriented to prevent malfunctions in the circuit. Double-checking connections helps catch any potential errors before powering the circuit.

After assembling the circuit, the next step is to connect the power supply. It’s essential to double-check that the power supply is turned off before making any connections. Once connected, you can turn on the power to supply the amplifier circuit with the necessary voltage (12V in this case). This step is crucial as it powers the NPN transistors and allows them to function.

Before proceeding to apply an AC input signal to the amplifier, it's important to verify the DC operating points (Q-points) of the transistors. This involves measuring the collector voltage (VC), base voltage (VB), and emitter voltage (VE) for both transistors (Q1 and Q2). These measurements should be recorded for later comparison with theoretical values, ensuring that the circuit is operating as expected.

After confirming that the amplifier is properly set up and functioning at DC, the next step is to introduce an AC signal. This is done using a Function Generator, which produces a sine wave at a specific frequency. It's advised to select a frequency where the amplifier's response is flat, usually in a mid-band area like 1kHz, with a low enough amplitude to keep the operation within the linear region of the amplifier to avoid signal clipping.

Once the AC input is applied, the next task is to measure the gain of each individual stage. This is achieved using an oscilloscope, which allows you to visualize the input and output signals. By measuring the input voltage (Vin) and the output voltage (Vout1) of the first stage, you can calculate the gain (AV1) using the formula: AV1 = Vout1 / Vin. It's also crucial to note the phase relationship between the input and output signals.

In this step, you measure the overall gain of the entire two-stage amplifier configuration. This involves connecting the oscilloscope to measure the input voltage of the first stage and the output voltage of the second stage. With these measurements, you can determine the overall gain (AV(total)) using the formula: AV(total) = Vout / Vin. Observing the phase relationship is also important to understand any phase shifts introduced by the amplifier.

After measuring the overall and individual stage gains, the next step is to compare the overall gain with the product of the individual stage gains, as AV(total) should theoretically equal AV1 × AV2, provided there are no significant loading effects between stages. This analysis will help identify any discrepancies due to loading or measurement errors.

Once all measurements and comparisons have been taken, it's important to properly power off the circuit. This includes turning off the DC power supply and the function generator to avoid any potential damage to the components or unnecessary power consumption. Proper shutdown is a best practice in electronic experimentation.