Feedback Amplifiers and Oscillators

<p>Series mixers combine the feedback signal with the input signal in series, while shunt mixers combine them in parallel. (D)</p> Signup and view all the answers

<p>To sample a portion of the output signal and feed it back to the input. (B)</p> Signup and view all the answers

<p>It can improve the stability, bandwidth, and noise performance. (B)</p> Signup and view all the answers

<p>$20 \log(101)$ (D)</p> Signup and view all the answers

<p>Current Series Feedback Amplifier (A)</p> Signup and view all the answers

<p>Increases input impedance (B)</p> Signup and view all the answers

<p>Transconductance with feedback is always less than transconductance without feedback. (A)</p> Signup and view all the answers

<p>Input impedance is increased due to series mixing. (C)</p> Signup and view all the answers

<p>$G_m_f = \frac{G_m}{(1+\beta G_m)}$ (A)</p> Signup and view all the answers

<p>Voltage sampling and series mixing (D)</p> Signup and view all the answers

<p>Output impedance decreases. (B)</p> Signup and view all the answers

<p>$R_{mf} = \frac {V_o}{I_s}=rac {V_o}{I_i+I_F}=rac{V_o}{I_i + \beta V_o}=rac {rac{V_o}{I_i}}{1+\beta rac{V_o}{I_i}}=rac{R_m}{(1+\beta R_m)}$ (C)</p> Signup and view all the answers

<p>The amount of signal fed back from the output to the input. (C)</p> Signup and view all the answers

<p>Gain with feedback is always less than the gain without feedback. (B)</p> Signup and view all the answers

<p>Feedback increases the amplifier's bandwidth. (A)</p> Signup and view all the answers

<p>Series feedback increases the input resistance. (A)</p> Signup and view all the answers

<p>Negative feedback reduces distortion by a factor of 1/(1+Aβ). (B)</p> Signup and view all the answers

<p>Shunt feedback decreases the input resistance. (C)</p> Signup and view all the answers

<p>To determine the amount of signal fed back from the output to the input. (C)</p> Signup and view all the answers

<p>Negative feedback decreases the output resistance. (A)</p> Signup and view all the answers

<p>When the gain without feedback (A) is very large, such that Aβ &gt;&gt; 1. (B)</p> Signup and view all the answers

<p>It reduces noise by a factor of 1 + Aβ. (C)</p> Signup and view all the answers

<p>The loop gain must be equal to 1. (B)</p> Signup and view all the answers

<p>Amplifying weak signals in audio circuits (A)</p> Signup and view all the answers

<p>Desensitivity is the reciprocal of sensitivity. (A)</p> Signup and view all the answers

<p>The loop gain must be 1 and the total phase shift must be 0° or 360°. (B)</p> Signup and view all the answers

<p>Negative feedback decreases gain and improves linearity. (C)</p> Signup and view all the answers

<p>180 (A)</p> Signup and view all the answers

<p>$hfe = rac{C_2}{C_1}$ (A)</p> Signup and view all the answers

<p>A Wien Bridge Network (C)</p> Signup and view all the answers

<p>$f = rac{1}{2\pi RC \sqrt{6}}$ (B)</p> Signup and view all the answers

<p>To amplify and filter the signal (B)</p> Signup and view all the answers

<p>To provide a starting point for oscillations (D)</p> Signup and view all the answers

<p>Colpitts oscillator (B)</p> Signup and view all the answers

<p>3 (A)</p> Signup and view all the answers

A circuit that samples and feeds back output signals to the input.

Feedback in phase with source signal that increases gain exponentially.

Feedback out of phase with source signal that reduces gain.

The measure of an amplifier's ability to increase signal strength.

The portion of the output signal fed back to the input.

The sampled output signal either in current or voltage form.

The range of frequencies over which the amplifier operates effectively.

The ability of an amplifier to maintain its performance over time or varying conditions.

An amplifier where output voltage is sampled and mixed in shunt.

Increased input impedance due to feedback, shown as R_m/(1 + βR_m).

The gain is adjusted to Af = A/(1 + Aβ), stabilizing output.

Total gain sensitivity reduced by feedback, calculated as 1 + Aβ.

Negative feedback reduces noise power by a factor of 1 + Aβ.

Reduces distortion in output to D_f = D/(1 + Aβ).

A coefficient that represents the portion of output fed back to input.

The voltage gain of the amplifier without any feedback applied.

The product of voltage gain (A) and feedback factor (β); describes feedback effect.

Measurement of feedback expressed in decibels; uses logarithmic formulas.

Categorized based on output signal sampling (voltage/current) and input signal mixing (series/shunt).

Samples output voltage and mixes in series; increases input impedance (Z_i) and decreases output impedance.

Samples output current and mixes in series; input impedance increases; also known as transconductance amplifier.

Transconductance adjusted by feedback; changes behavior in relation to input and output signals.

Samples output current and mixes in shunt; current is the monitored output parameter.

Determined by applying voltage at the output; it’s the voltage-current ratio.

The frequency range where amplifier gain is over 70.7% of maximum.

Calculated as BW = f_h - f_l, where f_h and f_l are the high and low frequencies.

Increased bandwidth, calculated as BW_f = BW (1+Aβ).

Increases input resistance: R_if = R_i (1+Aβ).

Decreases input resistance: R_if = R_i / (1+Aβ).

Decreases output resistance with increased load resistance.

A circuit that produces periodic waveforms without an input signal.

Conditions: Loop gain |Aβ| = 1 and phase shift around the loop is 0° or 360°.

The product of gain and feedback in an oscillator, important for oscillation sustenance.

The difference in phase between output and feedback signals, must be 0° or 360° for oscillations.

Random motion of free electrons due to thermal energy that initiates oscillations.

An oscillator using inductor and capacitor to generate oscillations with a specific frequency.

An LC oscillator type using an amplifier for a 180° phase shift and a tank circuit for another 180°.

An LC oscillator that achieves phase shift using two capacitors in the tank circuit.

An oscillator using resistors and capacitors, producing phase shifts for frequency generation.

An oscillator that uses a Wien bridge network and requires an amplifier gain of at least 3 for oscillation.