A preamplifier circuit with a very low noise characteristic can be built by simply combining a FET transistor with a bipolar one. The input impedance of the preamp circuit is almost the same as the gate impedance of the FET transistor (around 1MΩ) The output impedance at the other end is about 1KΩ.

1. PRE AMPLIFIER
KAROLINEKERSIN.E
ASSISTANT PROFESSOR

2. AMPLIFIER
 Amplifier is an electronic circuit or device which is used
for amplification purpose and used mainly in sound
reproduction as well in our electronic industry widely.
 There are many types of amplifier available by using
different components like transistor based amplifier, op-
amp based amplifier, transformer based amplifier.

3.  A preamplifier (preamp or "pre") is an electronic
amplifier that converts a weak electrical signal into an
output signal strong enough to be noise-tolerant and
strong enough for further processing, or for sending to a
power amplifier and a loudspeaker.
 Without this, the final signal would be noisy or distorted.
 They are typically used to amplify signals from analog
sensors such as microphones and pickups.
 Because of this, the preamplifier is often placed close to
the sensor to reduce the effects of noise and
interference.
PRE AMPLIFIER

4. PRE AMPLIFIER
• Transistor BC547
• Bread Board
• 8ohm Speaker
• 100uF capacitor
• Power Supply
• Resistor 2.2k
• Aux wire or audio
jack or MIC
• Connecting wire
• Jumper wire

5.  Here the capacitor C1 is acting as coupling
capacitor. Coupling capacitor is used as a
filter to block out the DC component of the
input signal, thus also called as DC blocking
capacitor.
 It prevents the headphones or speaker to
get damaged by the DC flowing of current.
PRE AMPLIFIER

6.  Transistors can be used either as a switch
or as a amplifier.
 So here this NPN Transistor BC547 is acting
as Amplifier.
 In amplification setup, this transistor allows
larger current to be flowed when smaller
voltage is applied at its base.
 So here voltage is applied at its base
through the audio input signal by AUX jack
and it allows larger current to be passed
from the 9v battery source thought the
speaker.
 In that way it is converting Electric energy
into audio output.

7.  Impedance matching is defined as the process of
designing the input impedance and output
impedance of an electrical load to minimize the
signal reflection or maximize the power transfer
of the load.
 An electrical circuit consists of power sources like
amplifier or generator and electrical load like a
light bulb or transmission line have a source
impedance.
 This source impedance is equivalent to
resistance in series with reactance.
IMPEDANCE MATCHING

8. IMPEDANCE MATCHING
CIRCUIT

9. Consider that, the Resistor (R) and Inductor (L) are in
series. And this combination is in parallel with the
Capacitor (C). Hence, the Impedance is,

10. Separate the imaginary part and real part of the above
equation with the help of complex conjugate.

12. At ω = ω0, we have resistance for Yin, which should be set
to R’.

13. Impedance Matching Applications
In electrical and electronic circuit design, the main goal
of a designer is to achieve maximum power that can
deliver from the source to load.
In almost all applications, impedance matching is
necessary.

14. THANK YOU