Original Assignee Oki Electric Industry Co Ltd Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.) Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) Expired - Lifetime Application number US07/748,661 Inventor Seiichi Yamazaki Current Assignee (The listed assignees may be inaccurate. Google Patents Constant-current source circuit having a mos transistor passing off-heat currentĭownload PDF Info Publication number US5180967A US5180967A US07/748,661 US74866191A US5180967A US 5180967 A US5180967 A US 5180967A US 74866191 A US74866191 A US 74866191A US 5180967 A US5180967 A US 5180967A Authority US United States Prior art keywords current mos transistor coupled fixed voltage voltage terminal Prior art date Legal status (The legal status is an assumption and is not a legal conclusion. Google Patents US5180967A - Constant-current source circuit having a mos transistor passing off-heat current The second file shows the frequency-dependent impedance at 65 V and 7.5 mA, where the dashed line on the right is the capacitive reactance of 18.2 pF (important at higher audio frequency).US5180967A - Constant-current source circuit having a mos transistor passing off-heat current
At higher frequency, the capacitance shunts the resistive component. The first attached file is my measurement of the dynamic resistance of the circuit (as a function of DC current), measured at DC between 10 and 20 V.
The data sheet is at I like them because of their high voltage rating and ease of use. The initial source resistor was chosen to be a bit large, and I determined a shunt resistor to trim the current to the correct value by connecting a decade box in parallel with it to find the appropriate final resistor. (I used them as 6 mA plate loads with Nuvistor triodes in audio amplifiers, and as a current regulator into a string of Zener diodes at 85 mA with an appropriate heat sink.) I assembled them with a gate-stopper resistor and a source-feedback resistor to a standoff screwed to the drain tab for low power, or mounted on a heat sink for higher power.
It is based on a depletion-mode MOSFET, using a resistor in the source lead to set the current with the gate-source voltage. I have used successfully the IXYS IXCP10M45S as a floating two-terminal constant-current device (see Fig 1 of the data sheet cited below).
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