Hi Antoinel
Trafo PCF and/or bootstrap connection for DEf and Vfet amplifier's that superb interesting option
***** Have a nice day
*****
The attached schematic shows another circuit for an auto-former passive gain block. The primary winding of the auto-former is wired as a bridge tied load [BTL] to/of two preamplifiers; whereby their two output signals driving the primary winding it are 180 degrees out phase. The output voltage [Vo] of this auto-former circuit to the input of a diyDEF may range between [8-16] times that of Vin.
The Pass preamplifier described by DIYer juma in his thread "LSK pre-BAF 2013' has in principle 2 outputs which are 180 degrees out of phase with each other. It is most probably useable in this application. The value of the load resistor at its normal [inverted] output will need to be trimmed so as to make both output signals equal in absolute amplitude.
The Pass preamplifier described by DIYer juma in his thread "LSK pre-BAF 2013' has in principle 2 outputs which are 180 degrees out of phase with each other. It is most probably useable in this application. The value of the load resistor at its normal [inverted] output will need to be trimmed so as to make both output signals equal in absolute amplitude.
Attachments
Hi Zen Mod. My apology for not calling the schematic "simplified". I should have been more explicit as follows. Thanks for your constructive comment.
The non-inverting [LSK] preamp output is the joined sources of the input complementary JFETs which connect to ground via a suitable resistor. The voltage gain at the joined sources of the input JFETs is unity.
The inverting [LSK] preamp simultaneous output is the joined collectors of the complementary BJTs connected in a folded cascode configuration. This junction of opposed BJT collectors goes to ground via a second resistor which determines the inverted output gain of the inputsignal .
The value of this second resistor needs to be lowered so as to deny this second [folded cascode] stage a voltage gain and essentially make it unity. Thus both outputs will have identical unity gain for their respective Vout; but are 180 degrees out of phase.
The joined gates of the front end complementary JFETs are connected to ground via a resistor which determines the input impedance to Vi which is referenced to common or ground.
As a concept yes, but finding Vgs matches at 1.5 A at temperature between
a depletion mode part and an enhancement mode is tedious at best.
The R085's are in spitting distance of common P channel enhancement mode
parts like Fairchild, IR, and Harris, and even then it took me a couple days to
get a small batch.
Of course I was shooting for no degeneration and no adjustment...
a depletion mode part and an enhancement mode is tedious at best.
The R085's are in spitting distance of common P channel enhancement mode
parts like Fairchild, IR, and Harris, and even then it took me a couple days to
get a small batch.
Of course I was shooting for no degeneration and no adjustment...
