Electronics

State the name of this type of amplifier.

Show that the gain of the amplifier is 6.0.

At time $t = 0$ the input potential $V_{IN}$ is zero. $V_{IN}$ then gradually increases with time $t$ as shown in Fig. 7.2.

On Fig. 7.2 sketch a line to show the variation with time $t$ of the output potential $V_{OUT}$ from time $t = 0$ to time $t = T$.

State how the circuit of Fig. 7.1 may be changed so that the gain of the amplifier is dependent on light intensity.

State the name of the component used as the output device of the op-amp.

Complete Fig. 7.3 using the device named in (i) and a diode so that the heater may be switched on when the output of the op-amp is positive.

Calculate the potential $V^+$ at the non-inverting input of the op-amp.

$V^+$ = ______ $\text{V}$

At $10^\circ\text{C}$, the resistance of the thermistor is $2.5\ \text{k}\Omega$.

State and explain whether the light-emitting diode (LED) is emitting light.

Explain why the student’s circuit will not indicate any change in temperature above $0^\circ\text{C}$.

The resistor of resistance $5.0\ \text{k}\Omega$ is changed to a resistor of resistance $R$ so that the LED switches on or off at a temperature of $20^\circ\text{C}$.

Determine $R$ in $\text{k}\Omega$.

$R$ = ______ $\text{k}\Omega$

infinite input impedance

infinite bandwidth.

Show that the potential at point X is $0.40\ \text{V}$.

The thermistor has a resistance of $360\ \text{k}\Omega$ at a particular temperature.

For this temperature of the thermistor, calculate the magnitude of the reading on the voltmeter.

voltmeter reading = ______ $\text{V}$

The temperature of the thermistor increases.

State and explain the effect of this change on the magnitude of the reading on the voltmeter.

Explain why the amplifier circuit will no longer indicate temperature changes when the magnitude of the gain of the circuit is greater than $12.5$.

Calculate the potential $V^+$ at the non-inverting input of the op-amp.

$V^+$ = ______ $\text{V}$

At $10\ ^\circ\text{C}$, the resistance of the thermistor is $2.5\ \text{k}\Omega$.

State and explain whether the light-emitting diode (LED) is emitting light.

Explain why the student’s circuit will not indicate any change in temperature above $0\ ^\circ\text{C}$.

The resistor of resistance $5.0\ \text{k}\Omega$ is changed to a resistor of resistance $R$ so that the LED switches on or off at a temperature of $20\ ^\circ\text{C}$.

Determine $R$ in kΩ.

$R$ = ______ $\text{k}\Omega$

State two properties of an ideal operational amplifier (op-amp).

Fig. 7.1 shows a circuit that includes an ideal op-amp and two identical resistors R.

State the names of components X and Y.

X: ______ Y: ______

Explain why the op-amp in Fig. 7.1 has only two possible output states.

State the name of the type of op-amp circuit in which the op-amp behaves as in (c)(i).

Describe the environmental condition under which the lamp L in Fig. 7.1 will light.

Suggest the purpose of the variable resistor V in the circuit.

An operational amplifier (op-amp) has two input terminals and one output terminal.

State what is meant by the gain of an op-amp.

State two effects of negative feedback on the gain of an amplifier circuit that uses an op-amp.

1. ______

2. ______

State the name of the type of circuit shown in Fig. 7.1.

On Fig. 7.1, label with the letter X a point in the circuit that is considered to be a virtual earth.

Calculate the gain of the circuit in Fig. 7.1.

gain = ______

Determine the value of $V_{IN}$ when $V_{OUT}$ is $+6.5\text{ V}$.

$V_{IN}$ = ______ $\text{V}$

Determine the value of $V_{OUT}$ when $V_{IN}$ is $-5.4\text{ V}$.

$V_{OUT}$ = ______ $\text{V}$

State two properties of an ideal operational amplifier (op-amp).

Fig. 7.1 shows a circuit that includes an ideal op-amp and two identical resistors R.

State the names of components X and Y.

X: ______ Y: ______

Explain why the op-amp in Fig. 7.1 has only two possible output states.

State the name of the type of op-amp circuit in which the op-amp behaves as in (c)(i).

Describe the environmental condition under which the lamp L in Fig. 7.1 will light.

Suggest the purpose of the variable resistor V in the circuit.

State, by reference to the input and output signals, the function of a non-inverting amplifier.

the gain of the amplifier circuit

gain = ______

the resistance of resistor R.

resistance = ______ $\Omega$

suggest a suitable device to connect to the output such that the shape of the waveform of the sound received by the microphone may be examined

state and explain the effect on the output potential difference $V_{\text{OUT}}$ of increasing the resistance of resistor R.

what is meant by infinite bandwidth

the effect, if any, on the output voltage of increasing the load resistance.

Explain why point $P$ is known as a virtual earth.

Calculate the potential at point $Q$.

potential = ______ $\text{V}$

At a temperature of $13^\circ\text{C}$, the resistance of the thermistor $T$ is $230\ \text{k}\Omega$.

Show that the potential difference measured with the voltmeter is $0.88\ \text{V}$.

The resistance of the thermistor $T$ in (b) decreases as its temperature rises.

Explain the effect of this change in temperature on the potential difference measured with the voltmeter.

State, by reference to the input and output signals, the function of a non-inverting amplifier.

the gain of the amplifier circuit

$\text{gain}$ = ______

the resistance of resistor R.

$\text{resistance}$ = ______ $\Omega$

suggest a suitable device to connect to the output such that the shape of the waveform of the sound received by the microphone may be examined

state and explain the effect on the output potential difference $V_{\text{OUT}}$ of increasing the resistance of resistor R.