4423

SBFS020A − JANUARY 1978 − REVISED JUNE 2004

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7

For example, the DF of ceramic disc capacitors is on the

order of 3%, which for a 0.01

µF capacitor would be

comparable to an internal resistor of 530k

Ω at 1kHz.

The 530k

Ω value resistor is small enough to stop the

4423 oscillator from oscillating.

Some capacitor manufacturers use the terms Power

Factor (PF) or Q Factor (Q) instead of dissipation factor.

These

terms

are

similar

in

meaning

and

are

mathematically related by Equations (5) and (6).

(PF)

+

(DF)

1

Q

+ 1

(DF)

OSCILLATION AMPLITUDE

It takes a finite time to build up the amplitude of the

oscillation to its final full-scale value. There is a

relationship between the amplitude build-up time and

the frequency. The lower the frequency, the longer the

amplitude build-up time. For example, it typically takes

250 seconds at 1Hz, 30 seconds at 10Hz, 4 seconds at

100Hz, 400 milliseconds at 1kHz, and 40 milliseconds

at 10kHz oscillator frequencies.

There are two methods available to shorten this normal

amplitude build-up time. There is also a relationship

between the amplitude build-up time and distortion at

final amplitude value. When the amplitude build-up time

is shortened, the distortion can become worse.

One method to shorten the amplitude build-up time is to

connect a resistor between pin 3 and pin 14. The lower

the value of this resistor, the shorter the time to build up

amplitude of the oscillation. Conversely, the distortion

of the output waveform worsens. For example, a 100k

Ω

resistor would shorten the amplitude build-up time,

from 15 seconds to 1 second at 20kHz frequency, but

the distortion could be degraded from typically 0.05% to

0.5%.

The other method is to momentarily insert a 1k

Ω

resistor via a reset switch between pin 3 and pin 14. The

amplitude of oscillation is built up instantaneously when

the reset switch is pushed. There will be no degradation

of distortion with this method since the 1k

Ω resistor

does not remain in the circuit continuously.

(5)

(6)