3.1 Name ONE type of field-effect transistor (FET) - NSC Electrical Technology Electronics - Question 3 - 2021 - Paper 1

One application of a MOSFET other than an amplifier is in digital switching circuits, where it acts as a switch to control the flow of current.

Region Y is the negative resistance region, while region Z is the forward-active region in the UJT characteristic curve.

Point D corresponds to the point where the device transitions from the cut-off region to the saturation region, indicating the start of conduction.

At cut-off point B, the reverse leakage current is minimal, which means that the unijunction transistor is in a non-conductive state, effectively blocking any significant current flow.

Four characteristics of an ideal operational amplifier are:

1. Infinite open-loop gain.
2. Infinite input impedance.
3. Zero output impedance.
4. Infinite bandwidth.

The voltage gain (A_v) of a non-inverting amplifier is calculated using the formula: $A_v = 1 + \frac{R_F}{R_N}$ Substituting the values, we get: $A_v = 1 + \frac{50 kΩ}{10 kΩ} = 6.$

The output voltage ($V_{out}$) can be calculated using the formula: $V_{out} = A_v \times V_{IN}$ Substituting the values, we find: $V_{out} = 6 \times 1.5V = 9V.$

Decreasing the feedback resistor $R_F$ will increase the voltage gain of the amplifier, possibly pushing it closer to saturation. This may affect stability and linearity in the output signal.

Pin 2 on the 555 timer IC is the Trigger pin.

The function of pin 6 (threshold) on a 555 IC is to monitor the voltage level of the timing capacitor. When this voltage exceeds 2/3 of the supply voltage, it resets the flip-flop and consequently the output state.

The 555 timer IC can operate from power supply voltages of between +5 V and +18 V.

In astable mode, the 555 timer continuously toggles between its high and low states, generating a square wave output. This mode is often used for clock pulses and timers.