CMV1030 查看數據表（PDF） - California Micro Devices => Onsemi

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CMV1030

MICROPOWER RRO Operational Amplifier

California Micro Devices => Onsemi 

CMV1030

ingly.

Figure 2.

4. Capacitive Load Considerations

The CMV1030 is capable of driving capacative loads in

excess of 100pF without oscillation. However, significant

peaking will result. Probably the easiest way minimize

this problem is to use an isolation resistor as shown in

Figure 3.

shown in Figure 4 provides a stable frequency operating

from a single supply voltage and drawing a mere 40µA.

For (R1 + R2) ÷ R1 = 0.473, the period, T, of the oscillator

is given by:

T = 2R C

F1

Where: RF is the feedback resistor

C1 is the capacitor

The period is easily adjusted by varying RF. R3 ensures

that the circuit will start on a single rail by forcing A1’s

output to the positive rail. R4’s value is not critical but

should be a factor of 10 greater than the parallel combi-

nation of R1 and R2. The circuit lends itself to a variety of

applications such as battery operated toys where a

stable frequency is required and low supply current is a

must to maintain battery life.

Figure 3

5. Power Supply Decoupling

The CMV1030 is not prone to oscillation without the

use of power supply decoupling capacitors, however to

minimize hum and noise pick-up, it is recommended that

the rails be bypassed with 0.01µF capacitors.

6. Typical Applications

Operational amplifiers have been used for years to

generate frequency stable oscillators, but the circuit

Figure 4

Personal Computers including laptops are available with

sophisticated and high quality audio capabilities. Battery

conservation is a key issue with laptop computers, and

the circuit in Figure 5 utilizes the low supply current of

the CMV1030, its rail to rail output voltage swing, and its

high output current drive to provide the interface to the

microphone input. A1 is used to provide the common

mode bias for A by buffering the V output (typically

2

REF

2.2 volts) of the Codec and to supply bias to the micro-

phone. R should be selected for the appropriate bias for

1

the microphone. R3 and C2 provide low pass filtering for

noise, and the closed loop gain of A2 is adjusted by the

ratio of R5 to R4.

© 2000 California Micro Devices Corp. All rights reserved.

215 Topaz Street, Milpitas, California 95035  Tel: (408) 263-3214

Fax: (408) 263-7846

www.calmicro.com

10/19/2000

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