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# AE_Lecture4_PartD1_Time_Domain_Response

Module by: Bijay_Kumar Sharma. E-mail the author

Summary: This gives the definition of Frequency Domain & Time Domain response of an Amplifier.

Analog Electronics_Lecture4_PartD

Experimental Methods of measuring

the Frequency Band-Width of an Amplifier.

There are two methods of determining the frequency Band Width (BW) of any amplifier:

1. Frequency Domain Response method and
2. Time Domain Response Method.

Frequency Domain Response

Figure 1. Block Diagram of an Electronic System(Amplifier) connected to the source at the Input and to the Load at the Output.

Plot of

vs Frequency - magnitude frequency response ;

Plot of

vs frequency - phase angle frequency response.

Both together constitute the Frequency domain response.

Time Domain Response

When we apply square wave and measure the rise time(tr) at high frequency and measure the sag (10% sag frequency) at low frequency then we say that we are looking at time domain response.

1. Rise Time Method of determining the upper -3dB frequency.

Figure 2. Square Wave Input into an amplifier gives a response from which Time Domain studies can be done.

Figure 3. Square Wave Response of an Amplifier at high frequencies. Because of upper -3dB frequency the leading and lagging edges get rounded off. At the leading edge rise time and at lagging edge fall time is introduced.

NOTE: At the leading edge we measure the rise time and at the lagging edge we measure the fall time.

1. DETERMINATION OF LOWER -3dB FREQUENCY(f L ) BY TIME DOMAIN METHOD

Figure 4. Square Wave Response of the Amplifier at low frequencies gives a sag at the top and bottom as shown below.

Figure 5. Square Wave Response of the Amplifier at low frequencies. % Sag = (∆V/V 0 )×100 where V 0 is peak to peak amplitude and ∆V is the tilt at the top or at the bottom.

(∆V/V 0 )×100 = % sag.

The p.r.f is adjusted to f* to obtain 10% ag then f L = (0.1f*/π).

Where f L = lower -3dB frequency.

High frequency suppression leads to the rounding off the leading and the lagging edges of the square wave.

Low frequency suppression leads to the sag of the top and bottom of the square wave.

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