Section 3: Audio amplifier [6 marks] Use the following naming convention: STDNUM_A_amplifier.asc The following circuit i

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Section 3 Audio Amplifier 6 Marks Use The Following Naming Convention Stdnum A Amplifier Asc The Following Circuit I 1 (202.72 KiB) Viewed 43 times

Section 3: Audio amplifier [6 marks] Use the following naming convention: STDNUM_A_amplifier.asc The following circuit is that of a class A amplifier. The design process follows with questions at the end VCC VCC VCC RI <R3 V out ci Vin F 01 + c2 > R2 < >R4 Figure 6: Schematic of an A class amplifier To design and build this A class amp we need to: • Decide on the collector/emitter current. As an example, consider picking 1 mA. • Decide on a Ve (The voltage on the emitter - above the emitter resistor). If we pick too small voltage, the tolerance errors in the resistor affects the actual current flowing. Picking too large a Voltage on Ve reduces the voltage available above the transistor which reduces our output voltage (Vout ) swing. Let's pick Ve = 1.5 V for now. • Choose a gain for the overall circuit which determines the value of Rcollector. If we pick a gain of 3, then the emitter resistor below the transistor forces an le which is closely linked to Ic + Ip = le (We often ignore the base current as the worst case B for a signal transistor is 100 minima which makes the base current negligible). Assuming the same current, similar to a voltage divider if the resistor is bigger, then there is a bigger voltage swing. The gain therefore becomes RE Rcollector = 3. So, we now have Remitter the resistor value. = R4 • Finally, the voltage divider producing the necessary bias voltage to the base of the transistor. We know Ve as we chose it, which means we also know Vo = Ve + 0.7V.le is known and therefore know (worst case) Ib. If we ensure that Ib is less than 1% of the current flowing through our voltage divider, then it can be considered negligible. Given the information about the class A amplifier, what are the values of Rcollector and Remitter? Simulate this on LTSpice and include this in your submission. You will have to determine the value of the capacitor as well with reasoning. Show your calculations for all component values. (Make sure it is in the E12 series) [6 marks