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| Simple DIY Linear PSU |
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| panoss:
--- Quote from: xavier60 on March 07, 2020, 08:47:54 am ---I would also expect the op-amps to be allowing Q1's Base voltage to go up much closer to 9V. Check this. Without knowing the current gain of the output transistors, I can't work out the expected maximum output current. You can try lower values for R10 as a temporary fix. Watch for stability problems. --- End quote --- With R10=1k: RL=5 Ohm, Q1: Vb=7.60V RL=10 Ohm, Q1: Vb=7.15V With R10=300 Ohm: RL=5 Ohm, Q1: Vb=6.43V RL=10 Ohm, Q1: Vb=6.13V With R10=300 Ohm it seems to work a lot better (it can give more current and voltage remains stable). For knowing the current gain of the output transistors I should simulate my first design? (the kakopa design from my first post?) |
| panoss:
--- Quote from: kallek on March 07, 2020, 09:15:16 am ---Next measure Q2 current to check if pass transistors get enough base current. --- End quote --- With RL=5 Ohms and R10=300 Ohms: Q2 Ie=0.147A Q3 Ib=0.0691A Q4 Ib=0.0691A |
| xavier60:
--- Quote from: panoss on March 07, 2020, 09:33:40 am --- --- Quote from: kallek on March 07, 2020, 09:15:16 am ---Next measure Q2 current to check if pass transistors get enough base current. --- End quote --- With RL=5 Ohms and R10=300 Ohms: Q2 Ie=0.147A Q3 Ib=0.0691A Q4 Ib=0.0691A --- End quote --- That works out to 20 for the output transistors. The simulator must be using the minimum spec from the data sheet. |
| xavier60:
150 for the driver transistor which is reasonable. A suitable value for R10 can be chosen after the design is built with real parts. |
| panoss:
So you 're saying the circuit is ok? I should built it and after this experiment with the value of R10? |
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