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Which of these doesn’t refer to a seriesshunt feedback?
In a series shunt feedback network, feedback is connected in series with signal source but in shunt with the load. Error voltage from feedback network is in series with the input. Voltage fed back from output is proportional to output voltage, hence parallel or shunt connected. The current in and voltage out connection refers to a shuntshunt connection.
Given that a feedback network is shuntseries, and output load is 10kΩ, what is the output voltage across it given that transfer gain is 10, source current is 20mA and feedback current is 10mA?
R_{L} = 10kΩ
I_{F} = βI_{L}
I_{L} = I_{F}/β = 10/10 = 1mA
V_{L} = I_{L}R_{L} = 10V.
Consider a voltage series feedback network, where amplifier gain = 100, feedback factor = 5. For the basic amplifier, input voltage = 4V, input current=2mA. Find the input resistance of the network.
R_{I} = V_{I}/I_{I} = 4/2m = 2kΩ
R_{IF} = R_{I}(1+A.β) = 2k(1+500) = 1002kΩ.
Consider the circuit shown below.
Consider A: Currentshunt feedback
B: Currentseries feedback
C: Voltageshunt feedback
D: Voltageseries feedback
Which of the above are present?
Resistor R5 causes global feedback. It is connected to the input node, causing shunt mixing but not to output node, meaning current sampling. Hence it’s a current shunt feedback. Resistors R6 and R7 are neither connected to input nor the output, causing series mixing and current sampling, hence causing current series feedback.
In a feedback network, input voltage is 14V, feedback voltage is 6V and source voltage is 20V. β is in ohms. What is its configuration?
Given that input is 14V, feedback is 6V and source is 20 V, we can see
V_{I} = V_{S} – V_{F}, which is voltage mixing. Also, β is in ohms that is voltage/current. Since output of feedback is voltage and input is current, the output has current sampling. Thus, configuration is a seriesseries feedback/current – series feedback.
In the following diagram, shaded portions are named A and B.
What are A and B?
When feedback network is in shunt with load, then output voltage appears as input to feedback. In above case, output current appears as the feedback input, hence B is a current sampling network. Also, feedback network is in shunt with the signal source, hence it’s called shunt mixing or current mixing.
Consider the circuit shown.
What is the type of sampling observed?
The feedback network is connected directly to output node, so voltage sampling occurs. However, it’s not connected directly to the input node. Hence it’s series mixing at the input. Voltage sampling is a shunt network.
In seriesseries feedback, the output is current sampled, that is it is in series with the load. Also, input is a voltage mixer, which is in series with signal source. So feedback factor
Β = V_{F}/I_{L} in Ohms.
In feedback systems, the feedback signal is in proportion with the output signal.
X_{F} ∝ X_{O}
X_{F} = βX_{O}, where β is the feedback factor or reverse transmission factor.
Consider an open loop circuit with lower cutoff frequency 5kHz and upper cutoff frequency 20kHz. If negative feedback is applied to the same, choose correct option stating the new cutoff frequencies.
Negative feedback decreases lower cutoff frequencies and increases the higher cutoff frequency.
f_{HF} = f_{H}(1+Aβ)
f_{LF} = f_{L}/(1+Aβ)
Total bandwidth is thus increased.
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