Strange LTP cascoding circuit

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
What are the role of D501 and D503 in this schematic?
Have something to do with high tempco of jfet ccs?
 

Attachments

  • kbl.jpg
    kbl.jpg
    93 KB · Views: 372
Mihai,

My mistake; I apologise, I was thinking of the highlighted capacitor between the LTP collectors!!'

These diodes are used to thermally compensate the BE junctions of TS15 and TS15 since both are fed from a current source and only one of the voltage reference diodes compensates the BE voltage of the CCS.

To be honest, I don't believe they are really necessary, particularly if you replaced the two diodes of the CCS with a green LED, which has almost the same tempco as the be junction of the CCS transistor.

Again, I'm sorry Mihai, I mistook the cap for your question!

Cheers,

Hugh
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.