CMV1010YR datasheet(9/10 Pages) CALMIRCO

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CALIFORNIA MICRO DEVICES

CMV1010

perfected by TV technicians in the 1950’s. A gimmick

is made by taking two lengths (typically about a foot)

of small gauge wire such as AWG24, twisting them

together, and then after baring all ends soldering the

gimmick across R

F. With the circuit operating, CF is

"adjusted" by clipping short lengths of the gimmick off

until the compensation is nominal. Then simply

remove the gimmick, take it to an impedance bridge,

and select the capacitor accordingly.

Figure 2

4. Capacitive Load Considerations

The CMV1010 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.

Figure 3

5. Power Supply Decoupling

The CMV1010 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

shown in Figure 4 provides a stable frequency operat-

ing from a single supply voltage and drawing a mere

40µA. For (R

1 + R2) ÷ R1 = 0.473,

the period, T, of the

oscillator is given by:

T = 2 R

F C1

Where: R

F is the feedback resistor

1 is the capacitor

The period is easily adjusted by varying R

ensures that the circuit will start on a single rail by

forcing A

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

critical but should be a factor of 10 greater than the

parallel combination of R

1 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 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 CMV1010, its rail to rail output

voltage swing, and its high output current drive to

provide the interface to the microphone input. A

1 is

used to provide the common mode bias for A

2 by

buffering the V

REF output (typically 2.2 volts) of the

Codec and to supply bias to the microphone. R

1 should

be selected for the appropriate bias for the micro-

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