Sound Pressure Meter(08-4c4)

7/29/2019 Sound Pressure Meter(08-4c4)

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ByV.Rakesh


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Introduction: This circuit is to setup home-cinema set

adjusting all the loudspeaker outputs to thesame level when heard from the listeningposition.

In practice this device is a simple (thoughlinear and precise) 100A ac millivolt meter.


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The CA3140A and CA3140 are integrated circuitoperational amplifiers that combine theadvantages of high voltage PMOS transistors withhigh voltage bipolar transistors on a singlemonolithic chip.

The CA3140A and CA3140 BiMOS operationalamplifiers feature gate protected MOSFET (PMOS)transistors in the input circuit to provide veryhigh input impedance, very low input current,and high speed performance.

The CA3140A and CA3140 operate at supplyvoltage from 4V to 36V (either single or dualsupply).


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These operational amplifiers are internally phasecompensated to achieve stable operation in unity gainfollower operation, and additionally, have access terminalfor a supplementary external capacitor if additionalfrequency roll-off is desired.

Terminals are also provided for use in applicationsrequiring input offset voltage nulling. The use of PMOSfield effect transistors in the input stage results incommon mode input voltage capability down to 0.5Vbelow the negative supply terminal, an important attribute

for single supply applications. The output stage uses bipolar transistors and includes

built-in protection against damage from load terminalshort circuiting to either supply rail or to ground.

The CA3140 Series has the same 8-lead pinout used forthe 741 and other industry standard op amps. TheCA3140A and CA3140 are intended for operation atsupply voltages up to 36V (-18v to +18v)


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The circuit is based on non- invertingamplifier based on op-amp CA3140 (IC1).

The sound picked by the condenser mic willbe amplified by the IC1 and rectified by thebridge D1 to drive the meter M1.

The deflection on the meter will be

proportional to the pressure of the soundfalling on the mic.

The switch S1 can be used as an ON/OFFswitch.


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The precision of the measure is entirelydepending on the frequency response of the

microphone used but, fortunately, for themain purpose of this circuit an absolutely flatresponse is not required.

Therefore, a cheap miniature electret

microphone can be used.


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THANK YOU

Sound Pressure Meter(08-4c4)

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