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High CMRR Instrumentation Amplifier (Schematic and Layout) design for biomedical applications

Instrumentation amplifiers are intended to be used whenever acquisition of a useful signal is difficult. IA’s must have extremely high input impedances because source impedances may be high and/or unbalanced. bias and offset currents are low and relatively stable so that the source impedance need not be constant. Balanced differential inputs are provided so that the signal source may be referenced to any reasonable level independent of the IA output load reference. Common mode rejection, a measure of input balance, is very high so that noise pickup and ground drops, characteristic of remote sensor applications, are minimized.Care is taken to provide high, well characterized stability of critical parameters under varying conditions, such as changing temperatures and supply voltages. Finally, all components that are critical to the performance of the IA are internal to the device. The precision of an IA is provided at the expense of flexibility. By committing to the one specific task of

Headphone Amplifier

 

Amplifier parts:

P1_____________22K   Log.Potentiometer (Dual-gang for stereo)

R1____________560R 1/4W Resistor
R2,R3__________10K 1/4W Resistors
R4_____________12K 1/4W Resistor
R5,R6___________2R2 1/4W Resistor
R7_____________22R 1/2W Resistor

C1______________1µF 63V Polyester Capacitor
C2,C3,C4______100µF 25V Electrolytic Capacitors
C5_____________22pF 63V Polystyrene or Ceramic Capacitor
C6_____________22µF 25V Electrolytic Capacitor

IC1___________LM833 or NE5532 Low noise Dual Op-amp

Q1,Q3_________BC337 45V 800mA NPN Transistors
Q2,Q4_________BC327 45V 800mA PNP Transistors

J1______________RCA audio input socket 
 

Power supply parts:

 
 
 R8______________2K2  1/4W Resistor

C7,C8________2200µF 25V Electrolytic Capacitors

D1____________100V 1A Diode bridge
D2____________5mm. or 3mm. Red LED

IC2___________7815 15V 1A Positive voltage regulator IC
IC3___________7915 15V 1A Negative voltage regulator IC

T1____________220V Primary, 15 + 15V Secondary 5VA Mains transformer

PL1___________Male Mains plug

SW1___________SPST Mains switch

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