16

The above CTR reduction must be considered when inserting a resistor between the emitter and the base of the phototransistor

of the optocoupler to increase the switching speed. The performance of the optocoupler might become unstable because the

CTR will be affected by time elapse or temperature change (even if it is initially stable).

Fig. 3-3 shows the

Normalized to 1.0

×

CTR = 274%

CTR =166%

1.0

0.8

0.6

0.4

0.2

0

100

200

300 400 500

1000

Ω)

Ω)

Ω)

Figure 3-3.

CTR = 274%

CTR =166%

1.0

0.8

0.6

0.4

0.2

0

100

200

300 400 500

1000

Normalized to 1.0

×

CTR = 274%

CTR =166%

Normalized to 1.0

×

1.0

0.8

0.6

0.4

0.2

0

100

200

300 400 500

1000