I would appreciate your thoughts as a sanity check for me, for the design below. Nothing new here, a preamp for low output sources (400mV to 1V - for a portable cdplayer and a guitar)the intention is to use some LSK489 I have, and 9V Vdd single supply. Gain of 2 should suffice.
I am going for a self-biasing topology, as basic as possible (for the time being at least). For 9V Vdd, I chose Idq=9mA for Vgs=-0.8V Datasheet says Vgsoff=-3V and rds=300 in my case, so Rs=330Ohm and Rd=367. Do these numbers sound right? I think there is enough headroom for the input signal I am interested in.
Any suggestions to convert mono to stereo? Like a cheap and cheerful transformer?
Is there an alternative to input and output capacitors?
Cheers!
I am going for a self-biasing topology, as basic as possible (for the time being at least). For 9V Vdd, I chose Idq=9mA for Vgs=-0.8V Datasheet says Vgsoff=-3V and rds=300 in my case, so Rs=330Ohm and Rd=367. Do these numbers sound right? I think there is enough headroom for the input signal I am interested in.
Any suggestions to convert mono to stereo? Like a cheap and cheerful transformer?
Is there an alternative to input and output capacitors?
Cheers!
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What confuses me is this: I chose 9V Vdd. Then looking at the characteristic curves, I picked the middle curve ie Vgs=-0.8V
For maximum swing I chose Vds=7V and Id=9mA
To find the Rs, I know that Vs=0.8V (Right?) This means Rs=VRs/Id=89 Ohm
To find Rd, Rd=VRd/Id. Also VRd=Vdd-(Vds+VRs)=9-(7+0,8)=> VRd=1,2V. So Rd=VRd/Id=1,2/0.009=.VRd=133.
This doesn't match with the previous post. And the issue is that rdson*Id=2,7V. Which I thought it should be equal to Vds. But when I drew the load line Vds was 7V.....
For maximum swing I chose Vds=7V and Id=9mA
To find the Rs, I know that Vs=0.8V (Right?) This means Rs=VRs/Id=89 Ohm
To find Rd, Rd=VRd/Id. Also VRd=Vdd-(Vds+VRs)=9-(7+0,8)=> VRd=1,2V. So Rd=VRd/Id=1,2/0.009=.VRd=133.
This doesn't match with the previous post. And the issue is that rdson*Id=2,7V. Which I thought it should be equal to Vds. But when I drew the load line Vds was 7V.....
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