Forums » General Electronics Discussion

1. can somebody help me with why the output of the below cct link with LED transmitting 2MHz RF is clipping. https://www.circuitlab.com/circuit/5j25n4/transmitter/#postsave_link_and_share

Or

This is my design

Vcc=10V, Vf(for LED)=1.5V. taking Vce=Ve=(10-1.5)/2=4.25V, Vbe=0.7V. Ic=If=Ie=50mA beta=200, Ib=Ic/beta=0.25mA. Re=Ve/Ie=85ohms.

R2=Vb/Ib=19.8k . Vb=Vcc*R2/(R1+R2) voltage divider where R1=19.4k.

if not correct need help from some one.

Thanks

pls disregard the previous post no link

There are several problems.

R1 & R1 are not connected to the transistor base. Hence, the base is not biased correctly.

The signal input is 10V pk-pk but you only have a 10V Vcc supply.

The positive part of the input voltage swing will be developed across the emitter resistor. The led will drop about 2V (Vd). The transistor will require a minimum of approx 0.25V Vce. Hence the max input swing to avoid clipping will be about Vcc-Vd-Vce.

The base will have to be biased so that the whole of the input signal swing is above approx 0.5V (Vbe).

Thank you signality. I corrected that and tried to rerun it is still clipping.Can you pls run it and see.

Your public circuit:

i.e.

https://www.circuitlab.com/circuit/5j25n4/transmitter/#postsave_link_and_share

is unchanged.