Hello GUYS,
Im in a big problem. Im working at 433MHz requency range. yesterday I was testing my circuit. I gave a dummy signal of 30MHz and 2Vp-p at the input of a peak detector. using the circuit shown in this link http://www.arrl.org/tis/info/pdf/0706060.pdf

I have kept the value of the resistor as 50ohm and the diode Im using is DO7 from farnell that has a voltage drop of 0.4v. The problem is the signal that comes out of the peak detector is only in the range of 700 to 800mv as it detects the peak voltage only. but this magnitude of voltage is not sufficient to trigger the 555 timer circuit that is there. As the timer circuit needs one-third of Vcc which is approx 1.6v.
COULD YOU PLEASE HELP ME WITH THIS....HOW DO I END UP INCREASING THE VOLTAGE THAT IS COMMING OUT OF THE PEAK DETECTOR SO THAT I CAN TRIGER THE 555TIMER. CAN I USE LM741 AS A VOLTAGE AMPLIFIER. PLEASE HELP ITS VERY URGENT.
THANKS
DIWAKAR

 

The 741 will work. Here is a link into our Ebook that shows how to set up one for gain - http://www.allaboutcircuits.com/vol_3/chpt_8/5.html.

 

To trigger the 555 the voltage must go below 1/3 of Vcc and not equal 1/3 of Vcc. Also, to trigger it, the trigger pulse must be a negative pulse. This means that the voltage on the trigger pin of 555 has to be over 1/3 of Vcc and then go below 1/3 of Vcc as to trigger the 555.

What is your 555 configuration?

 

Hello,

You can also use a comparator. The output swings when it goes over the desired level.
http://www.allaboutcircuits.com/vol_6/chpt_6/2.html

Greetings,
Bertus

 

the configuration in which Im using my timer555 is monostable to generate low and high signal for a period of 1 sec.