NCS2002 데이터 시트보기 (PDF) - ON Semiconductor

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NCS2002

Sub−One Volt Rail−to−Rail Operational Amplifier with Enable Feature

ON Semiconductor 

NCS2002, NCV2002

CT

1.0 nF

0.9 V

R1a

470 k

R1b

470 k

RT

470 k

0.9 V

−

+

R2

470 k

fO = 1.5 kHz

Output Voltage

Timing Capacitor

Voltage

VCC

0

0.67 VCC

0.33 VCC

The non−inverting input threshold levels are set so that

the capacitor voltage oscillates between 1/3 and 2/3 of

VCC. This requires the resistors R1a, R1b and R2 to be of

equal value. The following formula can be used to

approximate the output frequency.

fO +

1.39

1

RTCT

Figure 37. 0.9 V Square Wave Oscillator

cww 10 k

D1

1N4148

1.0 M

cw

CT

1.0 nF

D2

10 k

1N4148

VCC

−

+

VCC

R1a

470 k

R1b

470 k

R2

470 k

Output Voltage

Timing Capacitor

Voltage

VCC

0

0.67 VCC

0.33 VCC

Clock−wise, Low Duty Cycle

VCC

Output Voltage

fO

0

Timing Capacitor 0.67 VCC

Voltage 0.33 VCC

Counter−Clock−wise, High Duty Cycle

The timing capacitor CT will charge through diode D2 and discharge

through diode D1, allowing a variable duty cycle. The pulse width of the

signal can be programmed by adjusting the value of the trimpot. The ca-

pacitor voltage will oscillate between 1/3 and 2/3 of VCC, since all the

resistors at the non−inverting input are of equal value.

Figure 38. Variable Duty Cycle Pulse Generator

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