great!
I haven't played with the cascoded version, but I'm looking to get 25mA with 400V rails in a situation very similar to figure 1 in the datasheet., so just figuring out what needs to change for the cascoded version here. In the above schematic, are RSA and RSB the gate stopper resistors, "in" the anode and "out" the cathode, right? I've seen anything from 1k to 100R used for each of the gate stoppers and I'm supposing a 1k pot will work, or will these values need to be different with the two devices in parallel, and the graph on the datasheet doesn't apply here (i.e. for 25mA something other than 80R per the graph)?
thanks for the hand-holding!
I haven't played with the cascoded version, but I'm looking to get 25mA with 400V rails in a situation very similar to figure 1 in the datasheet., so just figuring out what needs to change for the cascoded version here. In the above schematic, are RSA and RSB the gate stopper resistors, "in" the anode and "out" the cathode, right? I've seen anything from 1k to 100R used for each of the gate stoppers and I'm supposing a 1k pot will work, or will these values need to be different with the two devices in parallel, and the graph on the datasheet doesn't apply here (i.e. for 25mA something other than 80R per the graph)?
thanks for the hand-holding!
RSA and RSB are stoppers. I have only used 1K, so I can't comment on how other values might work.
IN is the anode and OUT is the cathode. There are two OUT connections. MU is the mu follower connection, which you can ignore.
My experience is that the graph in the data sheet is not all that useful for determining current with the cascoded version. So, I'd start with a 500R, or 1K trimmer, and maybe a 20R resistor for R1, and then measure until you get the current you want. I typically set up one DMM in line to measure current. Then, connect a large resistor from OUT to ground and measure the voltage across it -- the combination will give you two different measures of current. I have a stack of $5 meters, and usually they are within a percent of each other doing this.
Do be careful while you do this. 400V is a lot of volts, and if that is on the cathode, then you will presumably have a few more on the anode. You'll need a string of resistors from out to ground to handle that voltage. Take some time to read the thread on safety practices, and make sure there is someone there with you. You might even use a lower supply to do the setting, and then drop them in the higher voltage circuit.
IN is the anode and OUT is the cathode. There are two OUT connections. MU is the mu follower connection, which you can ignore.
My experience is that the graph in the data sheet is not all that useful for determining current with the cascoded version. So, I'd start with a 500R, or 1K trimmer, and maybe a 20R resistor for R1, and then measure until you get the current you want. I typically set up one DMM in line to measure current. Then, connect a large resistor from OUT to ground and measure the voltage across it -- the combination will give you two different measures of current. I have a stack of $5 meters, and usually they are within a percent of each other doing this.
Do be careful while you do this. 400V is a lot of volts, and if that is on the cathode, then you will presumably have a few more on the anode. You'll need a string of resistors from out to ground to handle that voltage. Take some time to read the thread on safety practices, and make sure there is someone there with you. You might even use a lower supply to do the setting, and then drop them in the higher voltage circuit.
Trim pots
I'm sure there are many choices for the trim pot but I use these from Mouser. Part number 72-T93YA-value
Mouser catalog page 602
I'm sure there are many choices for the trim pot but I use these from Mouser. Part number 72-T93YA-value
Mouser catalog page 602
Donations Made
When all was said and done, there was about $150 left over from this group buy.
I donated $100 to the Tree House Animal Foundation, which is a cageless, no kill, shelter for cats in Chicago. If you like cats and happen to be in Chicago, it is worth a visit. Imagine a 3 story house with 300 or so cats roaming around.
I donated the other $50 to DIYAudio.
Thanks to everyone for your participation.
When all was said and done, there was about $150 left over from this group buy.
I donated $100 to the Tree House Animal Foundation, which is a cageless, no kill, shelter for cats in Chicago. If you like cats and happen to be in Chicago, it is worth a visit. Imagine a 3 story house with 300 or so cats roaming around.
I donated the other $50 to DIYAudio.
Thanks to everyone for your participation.
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