Hello, can somebody check my transistor amplifier schematic?

  • #76
434
19
They are critical. Those capacitors are not important to simulation but they are shown so they will not be forgotten when a real circuit is built.

One big problem with amplifiers, especially RF circuits, is when the output currents get back to the input stage which can then cause oscillation. So the design of the power supply as a low pass filter is as important as the design of the signal path.

It is important that multiple capacitors of different construction are used to bypass the supply. Electrolytics are slow and have high inductance so will need a faster capacitor closer to the circuit. Inside the circuit where active components connect to the power supply there will need to be fast ceramic capacitors, say 1nF.
Thank Your Sir
 
  • #77
434
19
They are critical. Those capacitors are not important to simulation but they are shown so they will not be forgotten when a real circuit is built.

One big problem with amplifiers, especially RF circuits, is when the output currents get back to the input stage which can then cause oscillation. So the design of the power supply as a low pass filter is as important as the design of the signal path.

It is important that multiple capacitors of different construction are used to bypass the supply. Electrolytics are slow and have high inductance so will need a faster capacitor closer to the circuit. Inside the circuit where active components connect to the power supply there will need to be fast ceramic capacitors, say 1nF.
sorry i come back one more time to you, now is working like your, because i was making exmperiments and i did, just the frequence i dont know they change from 90MHZ to 95MHZ, i dont know how to repair this one
 
  • #78
Baluncore
Science Advisor
8,487
3,203
1. I have no idea what you are wanting. What is broken? When did it last work OK? Are you considering an Ltspice or a SIMetrix simulation? Please give a link to the relevant circuit.

2. You do not have to quote a complete post to reply. Select the relevant part of the post, then right click to quote that small part only.
 
  • #79
434
19
1. I have no idea what you are wanting. What is broken? When did it last work OK? Are you considering an Ltspice or a SIMetrix simulation? Please give a link to the relevant circuit.

2. You do not have to quote a complete post to reply. Select the relevant part of the post, then right click to quote that small part only.
No my question, was the circuit you make it in LTSPICE, i make yesterday the same in SIMETRIX, i study your circuit in LTSPCIE,, after my circuits from yesterday is working perfect, Only the tuning is not working when i put probe to the cathode it changes the frequence from 90 to 100Mhz, i mean when i change the voltage at for .8V to 6.5V (is that normal working)?
here the circutis
LOCALOQCILLATOR WITHOUT FILTER3 GOOD.png
 

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  • #80
Baluncore
Science Advisor
8,487
3,203
You have tangled the varicap circuit.
I believe that your C4=42pF cap was used to represent the varicap circuit.
Remove C4=42pF.
Remove C10=100pF.
Connect varicap D1 cathode, to the open bottom node of L1.

Don't forget to remove the LPF.
 
  • #81
434
19
You have tangled the varicap circuit.
I believe that your C4=42pF cap was used to represent the varicap circuit.
Remove C4=42pF.
Remove C10=100pF.
Connect varicap D1 cathode, to the open bottom node of L1.

Don't forget to remove the LPF.
Goodmorning sir, i did not remove the c10(47p), because is not working, C4 i and lpf i remove, now with 2V is output 88MHZ AND 6.5V is 108Mhz, output to emitter of q2, thnx man:partytime:
 
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