With this circuit we can amplification selectively the high signal of picture frequencies [Video] with result bigger clarity than this. The circuit should be placed between a Video unit and the reception Scart or the plug Video input of television receiver. The designing is simple, it�s based in three only transistor. The first stage of Q1 function as isolator - adapter of input impedance. The second stage round the Q2 in common base connection which the gain is determined by the TR2. The TR1, R6 and C3 determine the frequency response. The third stage round the Q3 works as output buffer and 75-ohm line driver. The TR2 should be regulated in a place where the circuit output voltage, to be 1Vp-p, in 75 ohm load. The circuit functions with 12Volts - 50mA well stabilized. [Elektor 7/8 92
Pat List :
R1=82ohm R10=2.2Kohm C8=100nF 100V MKT
R2=5.6Kohm R12=180ohm TR1=250ohm trimmer
R3-9-11=2.7Kohm R13=68ohm TR2=500ohm trimmer
R4=330ohm C1-4-5=100uF 16V D1=1N4148
R5=220ohm C2=2200uF 16V Q1-2-3=BC547
R6=470ohm C3=470pF ceramic J1-2=Female RCA jack
R7=270ohm C6=470uF 16V J3=2pin connector 2.54mm step
R8=12Kohm C7=220uF 16V
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