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Description:
This
is a touch controled switch which keeps the circuit on about 100 seconds
after touching the plate connected to the 2 numbered pin. At the end of
this time duration, relay releases and the circuit gets to off
position.
The impedance of the trigger input of the 555 timer
IC is very high and the inductive voltage on the human body is enough
to trigger it. The circuit works based on this principle. You can use a
piece of metal as a plate. The circuit can be used in toy circuits,
buzzers or any project that is suitable. You can adjust the duration
time by changing the R1 and C1 values.
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Description:
This is a wide band amplifier circuit which is suitable for the frequencies between 10MHz and 500MHz.
Wide
band RF amplifiers are used in communication receivers, RF measuring
equipment and tons of other devices. The circuit described here uses a
state of the art transistor to get maximum performance at high
frequencies. It can be used as a low noise pre-amplifier due to his low
noise characteristics.
Amplifier Specifications:
Supply voltage : +12V
Current : 10mA
Input / output impedance : 50 Ohm
Frequency range : 10MHz – 500MHz
Noise figure : 3.5dB typical
IP2 : 110dBuV
IP3 : 105dBuV
This is a classical RF amplifier design. The feedback resistors R3
and R2 define the gain. By changing the values we can get a higher gain
at low frequencies, but this will influence the overall gain taper of
the amplifier. Coil L2 is used to get more gain at high frequencies. If
the value is increased, instability will occur...
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Description:
This is a PIN diode based attenuator circuit operates with 1MHz -
500MHz input.
PIN diodes are one of the most common parts used in RF applications
generally as switches in transmitter and receiver circuits. They are
usually placed at antenna or amplifier parts. In some applications PIN
diode functions not only as switch but also only as potentiometer.
Resistance of PIN diode is high when no current passing through it.
When current starts flowing, resistance decreases and diode conducts.
In this circuit we use PIN diode as a potentiometer. You can use this
circuit in a wide variety of applications. Some examples;
- Level control in signal generators
- Regulation of antenna signal at receivers
- Power control in RF amplifier drivers
- AGC control at receivers...
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