P2769

ETALDOC 332/14

Page 3 of 5

October 2007

Reference Circuit

In practice, the 100k

Ω load can be increased

without limit. The DC blocking capacitor should

be a minimum of 0.22µF to avoid resonance

within the voiceband to obtain a flat frequency

response and input impedance to specification.

40k

Ω APPLICATION CIRCUITS

For applications requiring impedance greater than 40kΩ for parallel-connected Terminal Equipment

(e.g. ETSI TS 103 021, ≥40kΩ, 200Hz – 4.3kHz) the following circuit may be helpful.

At the expense of a small loss, (approximately

1.5dBV) the circuit in fig. 3 provides an

impedance exceeding 40kΩ, 200Hz – 4.3kHz,

and frequency response flatness within ±0.25dB

over the same band.

Fig 2

100k

0.27µF

P2769

Fig 3

15k

33n

100k

P2769

Z > 40k

in

Ω