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

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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
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Mini Guitar/Bass Amplifier

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P1______________1M  Linear Potentiometer
P2____________100K  Log Potentiometer

R1_____________68K  1/4W Resistor
R2____________470K  1/4W Resistor
R3______________2K7 1/4W Resistor
R4______________8K2 1/4W Resistor
R5____________680R  1/4W Resistor
R6____________220K  1/4W Resistor
R7_____________39R  1/4W Resistor
R8______________2R2 1/4W Resistor
R9____________220R  1/4W Resistor
R10_____________1R  1/4W Resistor
R11___________100R  1/2W Resistor
R12_____________1K5 1/4W Resistor

C1____________100pF  63V Polystyrene or Ceramic Capacitor
C2,C5,C9,C14__100nF  63V Polyester Capacitors
C3____________100µF  25V Electrolytic Capacitor
C4_____________47µF  25V Electrolytic Capacitor
C6______________4n7  63V Polyester Capacitor
C7____________470pF  63V Polystyrene or Ceramic Capacitor
C8______________2µ2  25V Electrolytic Capacitor
C10___________470µF  25V Electrolytic Capacitor
C11____________22nF  63V Polyester Capacitor
C12__________2200µF  25V Electrolytic Capacitor
C13__________1000µF  25V Electrolytic Capacitor

D1______________3mm  red LED

Q1____________BF245 or 2N3819 General-purpose N-Channel FET

IC1_________TDA2003 10W Car Radio Audio Amplifier IC 

SW1,SW2________SPST toggle or slide Switches

J1____________6.3mm Mono Jack socket
J2____________6.3mm Stereo Jack socket (switched)
J3_____________Mini DC Power Socket

SPKR__________4 Ohm Car Loudspeaker 100 or 130mm diameter
 
 
 
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Tiny, portable Guitar Amplifiers are useful for practice on the go and 
in bedroom/living room environment. Usually, they can be battery powered
 and feature a headphone output.

This project is formed by an FET input circuitry, featuring a High/Low 
sensitivity switch, followed by a passive Tone Control circuit suitable 
to Guitar or Bass. After the Volume control, a 6W IC power amplifier 
follows, powered by a 12-14V dc external supply Adaptor or from 
batteries, and driving a 4 Ohm 10 or 13cm (4"/5") diameter car 
loudspeaker. Private listening by means of headphones is also possible. 
 
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  • Connect the output Plug of a 12 - 14V dc 500mA Power Supply Adaptor to J3
  • Please note that if the voltage supply will exceed 18V dc the IC will shut down automatically
  •  ***********************************************************
  • Output power (1KHz sinewave):
    6W RMS into 4 Ohm at 14.4V supply
    Sensitivity:
    50mV RMS input for full output
    Frequency response:
    25Hz to 20kHz -3dB with the cursor of P1 in center position
    Total harmonic distortion:
    0.05 - 4.5W RMS: 0.15% 6W RMS: 10%
    #################################################
    Tone Control Frequency Response: