Distributed amplifier
The distributed amplifier is an unconventional technique that allows an amplifier designer to escape the tradeoff between gain and bandwidth. With conventional amplifiers, if the gain of one stage is not enough, the designer has to cascade stages. The midband gain of the resulting two-stage amplifier is calculated by simply multiplying the midband gains of each of the stages. However, the bandwidth (3dB cutoff frequency) of the two-stage amplifier is lower than the bandwidth of each of the stages by itself. In most situations the resulting risetime, <math>t_r</math> is closely approximated by <math>t_r = \sqrt{t_{r1}^2 + t_{r2}^2}</math>, where <math>t_{r1}</math> is the risetime of the first amplifier and <math>t_{r2}</math> is the risetime of the second amplifier.
For example:
Amplifier 1:
- midband gain: 10
- risetime: 3ns
Amplifier 2:
- midband gain: 12
- risetime: 4ns
Cascade of Amplifier 1 and Amplifier 2:
- midband gain: 120
- risetime: 5ns