The circuit is incredibly useful. Some examples of uses cases are:<\/p>\n
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- Amplifier output stage grid drive<\/li>\n
- Screen drive amplifiers<\/li>\n
- Screen voltage stabiliser for pentode stages<\/li>\n
- HT voltage stabiliser for preamps<\/li>\n
- Buffer stage for high-mu\/high-anode resistance stages – either triodes or pentodes (e.g. Phono)<\/li>\n<\/ul>\n
PCB Features<\/h2>\n
Some key aspects of the board are:<\/p>\n
- \n
- The PCB has been designed to accommodate all sorts of power MOSFETs (both TO-220 and TO-247). In particular, the high transconductance and low Crss devices which perform the best in this role.<\/li>\n
- The tail CCS is simple and leverage the option of using same MOSFETs if wanted.<\/li>\n
- The board takes into account the use of a bipolar supply up to 300V differential. To set a source follower board, you only need to set the value of 2 resistors (CCS current and operating voltage) depending on the supply voltage levels, desired current sink and make sure there is a sufficiently big heatsink on the MOSFETs.<\/li>\n
- There is a current limiter circuit built in to protect screen or grid from excessive current. This is also very useful when the board is used as a voltage stabiliser for a preamp. You can limit the peak current and avoid destroying the top MOSFET when capacitors are charged or if accidentally the output is shorted. This circuit can be bypassed easily with a jumper.<\/li>\n
- PCB has been manufactured to high quality levels:\n
- \n
- FR4, 1.4mm thickness, ENIG finish, 2 Oz. copper.<\/li>\n
- PCB Dimensions: 25mm x 66.04mm<\/li>\n
- M3 mounting holes spacing\n
- \n
- Width: 20.32mm<\/li>\n
- Length: 60.32mm<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
Here is one of the boards submitted to the usual abuse during testing:<\/p>\n
![\"\"](\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2017\/07\/SF-board-under-test-768x1024.jpg?resize=525%2C700\")
<\/a><\/p>\nThis is a very useful PCB in my view which can be used extensively in preamps, line stages and amplifiers.<\/p>\n
![\"\"](\"https:\/\/i0.wp.com\/www.bartola.co.uk\/valves\/wp-content\/uploads\/2020\/05\/SF-PCB-Rev03-1.jpg?resize=768%2C1024&ssl=1\")
<\/a>SF PCB REv03\u00a0<\/figcaption><\/figure>\n Ordering the PCB<\/h2>\n
Please fill out the form below and I will get back to you once you confirmed quantity and shipping method (e.g. Standard or Tracked postage).<\/p>\n
Due to pandemic situation, USPS and other national post services have been a bit unreliable so I recommend tracked shipping where possible depending the value of the goods.<\/p>\n
Upon completion of payment, I will provide BOM and build guide.<\/p>\n
I don’t sell kits nor parts, appreciate your understanding. I may build and sell occasionally a few boards completed and tested, so ask me if you’re interested.<\/p>\n
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