Contents
What does a logarithmic amplifier do?
In general, the principal application of log amps is to measure signal strength, as opposed to detecting signal content. The log amp’s output signal, which can represent a many-decade dynamic range of high-frequency input signal amplitudes by a relatively narrow range, is typically used to regulate gain.
What is meant by multistage transistor amplifier?
In Multi-stage amplifiers, the output of first stage is coupled to the input of next stage using a coupling device. These coupling devices can usually be a capacitor or a transformer. This process of joining two amplifier stages using a coupling device can be called as Cascading.
What are the drawbacks of log amplifier?
This type of log amp has three disadvantages: (1) both the slope and intercept are temperature dependent; (2) it will only handle unipolar signals; and (3) its bandwidth is both limited and dependent on signal amplitude.
How does an oscillator differ from an amplifier?
The main difference between an amplifier and oscillator is that amplifier is a circuit that amplifies the input signal and an oscillator generates AC waveforms of a particular frequency that acts as a source for an electronic circuit. Oscillators generate periodic signals.
What kind of amplifier has a logarithmic characteristic?
This type of log amp can be considered to be a video amp with a logarithmic characteristic, and may be known as a logarithmic video ( log video) amplifier or, sometimes, a true log amp (although this type of log amp is rarely used in video-display-related applications). Figure 2-44:. Basic log amp (saturates with negative inputs)
When does a logarithmic AMP cease to function?
With inputs very close to zero, log amps cease to behave logarithmically, and most then have a linear V IN /V OUT law. This behavior is often lost in device noise. Noise often limits the dynamic range of a log amp.
Is there residual feedback in a logarithmic amplifier?
However carefully the amplifier is designed, there will always be a residual feedback capacitance, C C (often known as Miller capacitance), from output to input which limits the high frequency response. Figure 2-49:. AD538 block diagram
How is the gain of a multistage amplifier calculated?
The overall gain of a multistage amplifier is the product of the gains of the individual stages (ignoring potential loading effects ): Gain (A) = A 1 * A 2 *A 3 *A 4 *… *A n. Alternately, if the gain of each amplifier stage is expressed in decibels (dB), the total gain is the sum of the gains of the individual stages: