Refer to FIGURE 4.1 below of an inverting operational amplifier and answer the questions that follow - NSC Electrical Technology Electronics - Question 4 - 2023 - Paper 1

Op amps are rarely used in open-loop mode because their gain is extremely high, typically exceeding 100,000. This results in a very small input voltage creating a large output, making the system highly sensitive to noise and distortion, leading to instability and non-linear operation.

To calculate the voltage gain (A_v) of the inverting operational amplifier, the formula is given by:

$A_v = -\frac{R_f}{R_{in}}$

Substituting the values:

• $R_f = 1.2 k\Omega$
• $R_{in} = 1 k\Omega$

$A_v = -\frac{1.2 \times 10^3}{1 \times 10^3} = -1.2$

Thus, the voltage gain of the circuit is -1.2.

1. Resistor R_b sets the biasing point of the non-inverting input, allowing for stable operation of the amplifier.
2. It also assists in defining the input impedance of the circuit, impacting how the amplifier responds to varying signal conditions.

The voltage gain (A_v) for a non-inverting amplifier can be calculated using:

$A_v = 1 + \frac{R_f}{R_{in}}$

Given:

• $R_f = 120 k\Omega$
• $R_{in} = 10 k\Omega$

Substituting these values:

$A_v = 1 + \frac{120 \times 10^3}{10 \times 10^3} = 1 + 12 = 13$

Therefore, the voltage gain of the circuit is 13.

1. The 555 IC is commonly used in timer applications to create precise time delays.
2. It can also be utilized in pulse width modulation circuits for motor control.

1. The 555 IC has limited frequency response, making it unsuitable for high-speed applications.
2. It can consume more power compared to other modern timer circuits, affecting battery-operated designs.

Pin 4 of the 555 IC is the Reset pin, which is used to terminate the timing cycle. It allows external interrupts to function, resetting the timer even if it is currently active.

(a) The NPN transistor in the 555 circuit acts as a switch to control higher current loads based on the output signal from the timer. It allows external devices to be turned on or off at the specified timer interval.

(b) Comparator 2 in the 555 IC configuration is used to compare the input voltage against a reference level, enabling the detection of voltage thresholds necessary for starting or stopping the timing operation.