According to Borbely, zero tempco occurs at
Vgs = Vp + 0.63V
https://audioxpress.com/article/JFETs-The-New-Frontier-Part-1
Datasheet of JFE2140 specifies Vp as -0.9V ~ -1.5V.
Take the case of -0.9V. Vgs at zero tempco is -0.27V.
Fig. 6.1 of datasheet then implies zero tempco bias to be around 8mA.
Patrick
Vgs = Vp + 0.63V
https://audioxpress.com/article/JFETs-The-New-Frontier-Part-1
Datasheet of JFE2140 specifies Vp as -0.9V ~ -1.5V.
Take the case of -0.9V. Vgs at zero tempco is -0.27V.
Fig. 6.1 of datasheet then implies zero tempco bias to be around 8mA.
Patrick
I did a recent search for replacement N-channel JFETs used as switches in some vintage audio gear. The BEST I could find was a J109-D26Z with an Rds-on of 12Ω. In this application, N-channel enhancement MOSFETS (which require a + gate voltage to be on) will NOT work. Now I want to find a P-channel JFET switch with a similar low Rds-on. Any suggestions?
Most of the Pro Audio products I've been across used J175 (equiv to P1086 Interfet) and I believe even the potted Otari switching modules used them. Nowhere near your 12 ohms.
Which vintage gear?
Connecting "N" identical BJTs in parallel, the equivalent noise voltage is reduced by a factor of N^x (N raised to the power x). For bipolars, it turns out that x=(1/2). For example when N=4 identical BJTs are connected in parallel, equivalent input noise voltage is reduced by a factor of ( 4 ^ (1/2) ) = 2. Four parallel bipolars cuts equivalent input noise voltage by a factor of two.
What is the corresponding value of the exponent "x" when connecting N identical JFETs in parallel, rather than bipolars?
What is the corresponding value of the exponent "x" when connecting N identical JFETs in parallel, rather than bipolars?
I used the JFE2140’s in this in place of the LSK389 in the MM amplifier below and got superb results. Great JFET 👍
https://hifisonix.com/projects/x-altra-phono-eq-preamp/
https://hifisonix.com/projects/x-altra-phono-eq-preamp/
Could you simply parallel to two fets in the 2140 and have the same part in effect?
This does not really belong into this thread, it's just that I need it for an 2140
amplifier: Is there somewhere a Spice model of the THS3091 CFB opamp ???
It seems to be a happy combination of noise, 1/f corner and speed.
If it is on TI.com, then it's carefully hidden, at least in ASCII form. I'd prefer
Spice 3 format, best would be LTspice compatible, sorry, or Altium Designer,
or Keysight ADS, even if ADS would cost me bonus points with a customer. ;-)
Cheers, Gerhard
amplifier: Is there somewhere a Spice model of the THS3091 CFB opamp ???
It seems to be a happy combination of noise, 1/f corner and speed.
If it is on TI.com, then it's carefully hidden, at least in ASCII form. I'd prefer
Spice 3 format, best would be LTspice compatible, sorry, or Altium Designer,
or Keysight ADS, even if ADS would cost me bonus points with a customer. ;-)
Cheers, Gerhard
Thanks, I did find a zip archive somewhere on ti.com that
had lots of binaries and in a folder "timing simulation", there
was a netlist that included the model inline.
I snipped it off and put it into /d/libs/spice/gerhard_opa.lib,
but did not yet try it .
I think a spice model should belong into the data sheet. It is
much more important than the picture of card board box with a
reel of 5000. And it would help to keep the data sheet and
the model in sync. We all know to handle ctl-c/ctl-v in a .pdf.
cheers, Gerhard
had lots of binaries and in a folder "timing simulation", there
was a netlist that included the model inline.
I snipped it off and put it into /d/libs/spice/gerhard_opa.lib,
but did not yet try it .
I think a spice model should belong into the data sheet. It is
much more important than the picture of card board box with a
reel of 5000. And it would help to keep the data sheet and
the model in sync. We all know to handle ctl-c/ctl-v in a .pdf.
cheers, Gerhard