Don't you have a teacher and a text book like all other students have?
AM TRANSMITTER
modulations type am modulations
frequency range 1mhz
voltage supply 12v
transmitting distance 80m-100m
audio frequency 20hz-20khz
Don't you know that a 1MHz AM radio receives only about 50Hz to 3kHz? Why do you want 20kHz?
i know i need following circuit to make transmitter
-audio amplifier circuit
-Oscillator circuit
-RF amplifier circuit
-microphone
Then show us the circuits you designed for the transmitter.
i need circuit that amplify the signal of mic
There are hundreds of mic preamp circuits shown in Google.
i know to make amplifier circuit
transistor NPN, PNP transistor
mode ce, cb, ce
class A, B, C amplifier
Select the type of circuit then show it.
for design audio amplifier we select following parameters
audio source -microphone
transistor npn transistor
mode common emitter
class class A power amplifier
Then show it.
transistor ratings
collector emitter voltage=30v
collector base voltage=60v
emitter base voltage=5v
collector current=800mA
power=500mW
Almost ANY transistor can be an audio amplifier but yours does not have a part number.
Show us your circuit.
my questions
1. specification of microphone
frequency response
impedance
Select which type of microphone:
Electret or Dynamic.
2what is gain of audio amplifier
The gain required depends on the transmitter's modulator circuit.
3.which number of stages is used for audio amplifier
single stage
two stage transistor
It depends on the amplifier circuit and the amount of gain needed.
4.what is gain of rf amplifier
It depends on how much output power you need (and the sensitivity of the AM radio) and the amount of output level from the oscillator.
5.how we decide what gain is needed for signal
Use common sense.
6.which oscillator is used and what is frequency
wien bridge
colpit
crystal
You listed the frequency above. Weren't you taught about AM transmitters and high frequency oscillators?
7.what is length of antenna
For your very short range the antenna can be very short or be a ferrite bar like used in AM radios.
if possible please explain with mathematical calculations
Why didn't you learn them in school?