Power Amplifier

High impedene small amplifer circuit

This simple circuit was a presented,it can give power output about 1 watt, when connected to a power supply 9 volt. The advantage of this circuit is that it uses a dual darling ton to increase the size as much as of input impedance about 20 Meg ohm. This circuit unlike other circuits,the input impedance is a constant about 20 Meg ohm always, whether to adjust the volume control on any level.
The components in the circuit, it is cheap, especially the BC549 transistor output number when the increase will be very distorted, it must reduce the current level to a safe By reducing the volume down.
The sector output for the R1 and C1 in order to reduce the oscillator gain is, the fact that the output sector, including an op-amp acts drive dual complementary.

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Simple Amplifier circuit for converts the analog signal to digital

The electrical signals from transducer,Sometimes, it is value less too,For input to the circuit to convert signals from analog to digital.To achieve a satisfactory,We need a power amplifier, who can tell strength of the input signal is simple.This can extend the input signal from the transducer is 10 times and 100 times.
Circuit consists of op-amp IC1 No. 741,To give the appearance of non inverting circuit, R1 is configured input impedance switches.In this the 75 kilo ohms, negative feedback circuit consists of R3 or R4 together with R2, which defines the gain of the circuit.
Gain of the circuit is equal.
R2 + R3 / R2 When S1 scroll at the top.
R2 + R4 / R2 When S1 scroll down below.
When the value provided in the circuit will gain about 100 and 10 respectively (actually supposed to be 101 and 10.1).
Power supply for this circuit requires two sets of power supply positive and negative, which was in the range of positive, negative 6 volts to the positive, negative 15 volts, in this value add, subtract 9, because available with 9-volt battery immediately.

NTSC-PAL TV Signal Identifier

This circuit is able to identify PAL and NTSC video signals. Its output is high for an NTSC signal and low if the signal is PAL. This output signal can be used, for example, to automatically switch in a colour subcarrier converter or some other device while an NTSC signal is being received. One application is for the reception from satellites of ‘free-to-air’ TV signals, which in Australia generally contain a mixture of 625-line PAL and 525-line NTSC programs. Operation of the circuit is as follows. IC1 is an LM1881 video sync separator which takes the video input signal and generates vertical synchronisation pulses.

For an NTSC signal, these pulses are 16.66ms apart, corresponding to the 60Hz field rate, while for a PAL signal they are 20ms apart, corresponding to the 50Hz field rate. The vertical sync pulses are fed into IC2a, the first of two dual retriggerable monostable multivibrators in the 74HC123A. IC2a has a period of very close to 17.9ms, set by the 200kO resistor and 0.22µF capacitor at pins 14 & 15. Because the monostable is retriggerable, NTSC sync pulses arriving every 16.66ms will keep its Q output, at pin 13, high.[...]
Source : http://www.extremecircuits.net/2010/06/ntsc-pal-tv-signal-identifier_13.html

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