303 Mhz RF reciver circuit problem ..
i am makiing 303Mhz tx and Rx circuit.
i have a Rf receiver circuit diagram and i am trying to understand it.. but it has a inverter based amplifre stage which i dnt know why we use invertor to amplify and how inverter amplifies the signal and also in the reciver a there is a 32KHZ crystal which serve as detetion of frequency and i dnt know how crystal can b use for this purpose kindly guide me. thanks ...
Dear AliReza
Hi
Is that an FM transmitter ?
dear it is 303Mhz reciver but i am confused in 4069 amplifre stage and why we need and how crystal detect 32khz frequency and stop 303mhz carrier going further......
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dear it is 303Mhz reciver but i am confused in 4069 amplifre stage and why we need and how crystal detect 32khz frequency and stop 303mhz carrier going further......
I'm not 100% sure, but it looks like the inverter gates are being used as analog amplifiers (see here for an example).
Then, the 32kHz xtal is actually being used as a filter, not for an oscillator. See here for a similar discussion.
Hi again
I have asked that , is the modulation of transmitter FM ? if yes thus i can describe this circuit in detail . if the transmitter is kind of FM modulation , thus the not gates are used to remove noise .
I think it's AM.
The receiver is superregenerative, the 'UB' verisons of the inverters are Un-Buffered and being used as crude amplifiers. The 32KHz crystal is used as a filter so the modulation is achieved by adding a 32KHz signal to the transmission. The 32KHz is further amplified then rectified before driving the tone generator.
Brian.
Hi Brian
So , if it is an AM transmitter and then an AM receiver , can you describe how a not gate can works as a linear amplifier , please ?
Thank you
Goldsmith
The 'UB' version of the gate has a special proprty. It doesn't abruptly switch logic states, it has a region in it's characteristics where the output can be any voltage between VSS and VDD. It works rather like a high gain inverting amplifier rather than a logic gate. Because it is inverting, a resistor from the output pin to the input pin will bias it to mid-rail output just like an op-amp. They are highly non-linear and very noisy but for this application where other gates in the same package are needed elsewhere, it makes sense to utilize them as amplifier stages.
Brian.
Thank you dear Brian for that , i didn't know it . it is a new thing for me .
Best Regards
Goldsmith