Handbook for Sound Engineers

882 Chapter 25

strapped to high impedance via the 150: resistor at high
frequencies and the bootstrap voltage reducing (together
with its phase being shifted) with falling frequency. At
very low frequencies the capacitor behaves as a virtual
open circuit. No bootstrap exists, so the terminal is tied

to ground via the 150: resistor and the effectively zero

output impedance of the voltage follower. The circuit

emulates an inductor reasonably well; it has a low-

impedance value at low frequencies, increasing with

frequency to a relatively high impedance.

Figure 25-63. Inductive reactance synthesis.

Booster resistor

Terminal

Ground

Terminal

Ground

Terminal Bootstrap

C

R

A. Simplest inductance synthesis. B. Equivalent "real" circuits. C. Isolating parallel impedance.

Very

high

L

D. Equivalent circuit.

R

RS RF

Vin

C

R

Vo

E. Constant amplitude phase-shift network

Bootstrap/feedback resistor

RS RF

C

R

F. Bootstrap/feedback inductive

synthesis using CAPS network.

RS RF

Vin

Vo = Vin

Vin

G. Equivalent circuit of F. H. CAPS network E equivalent at very low frequencies.

J. Bootstrapped pair of CAPS networks (basic). K. Equivalent circuit of J.

RS RF RS RF

C

C

R

Terminal

R

C

L

I. CAPS network E at very high frequencies.

Bootstrap/feedback

Vo = Vin

Vo

RS RF

Very

high

R

L

100 K 7

150 7

150 7

100 K 7

150 7

MF

MF