The circuit posted here is of a preamplifier for ceramic pick-up having moderately high input impedance about 470Ω and voltage gain of more than 12.
Circuit Description of Preamplifier for ceramic-pickup
The circuit of a preamplifier for ceramic pickup is built around FETs because it has outstanding low-level characteristics including a high input impedance and low noise. These characteristics make the FET a natural choice at the input stage of a preamplifier for accepting signals from high-impedance transducers such as ceramic-pickup.
Inputs from the ceramic microphones are given to the base of FET through coupling capacitors C1. Vcc of 24V is given to the collector which senses the additional function of providing the base current. In this circuit bypass capacitors C2 offers an almost short circuit and prevents loss of amplification. Output is taken from the collector through capacitor C3 which is also coupling capacitors.
PARTS LIST OF PREAMPLIFIER FOR CERAMIC-PICKUP
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Resistor (all ¼-watt, ± 5% Carbon) |
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R1 = 470 KΩ R2 = 10 KΩ R3 = 3.9 KΩ |
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Capacitors |
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C1 = 0.1 µF (Ceramic Disc) C2 = 22 µF/12V (Electrolytic Capacitor) C3 = 10 µF/16V (Electrolytic Capacitor) |
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Semiconductor |
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T1 = BFW11 (N-Channel FET) |