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Transistor Types
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Several transistor types have been specified in various versions of this theremin. A summary appears in the following table:
Circuit Version |
PNP Transistor Type |
NPN Transistor Type |
N-channel JFET Type |
November 1967 Popular Electronics Feature |
Motorola MPS3638 |
Motorola MPS3708 |
Texas Instruments TIS59 |
Early Southwest Technical Products Kit |
Motorola MPS3638 |
Motorola MPS6566 |
Texas Instruments TIS58 |
Late Southwest Technical Products Kit |
(Generic) 2N5087 (note 2) |
(Generic) 2N5210 |
Texas Instruments TIS59 |
Schematic from http://www.nashville.net/~theremin/ |
(Generic) 2N5087 (note 3) |
(Generic) 2N5210 |
Texas Instruments TIS58 |
Text File from http://www.nashville.net/~theremin/ |
(Generic) 2N3906 |
(Generic) 2N3904 |
(Generic) 2N5457 |
144 Theremin |
(Generic) 2N3906 |
(Generic) 2N3904 |
(Generic) 2N5484 |
Notes:
1) A notice in a subsequent issue of Popular Electronics revises the type to TIS58. The critical parameter regarding this transistor in the application is the "gate-source cutoff voltage." This is specified as -0.5v to -5v for the TIS58 and -1v to -9v for the TIS59. The latter may be unsuitable, since a part exhibiting the -9v extreme may not function in this circuit. The TIS58 and TIS59 are no longer manufactured.
2) A notice provided with the later kits' instructions states:
"We are supplying later type transistors in your kit than those shown in the parts list. Instead of a 2N3638 you will receive a 2N5087 and instead of a MPS6566, you will receive a 2N5210. The later type parts being supplied have higher gain and will insure [sic] that the transistors will not be a problem in the operation of this circuit."
The reference to type "2N3638" was probably an error; they likely meant "MPS3638."
The MPS3638 has an hFE specification of 20 minimum at Ic=10mA and Vce=10v, whereas the 2N5087 has an hFE specification of 250 minimum at Ic=0.1 to 10mA and Vce=5v.
The MPS6566 has an hFE specification of 100 minimum at Ic=10mA and Vce=10v, whereas the 2N5210 has an hFE specification of 250 minimum at Ic=1mA and Vce=5v.
3) The PNP and NPN transistor symbols' leads in this schematic are labeled "1" for the collectors, "2" for the bases, and "3" for the emitters. This is contrary to manufacturers' data, which designates pin 1 for emitters, pin 2 for bases, and pin 3 for collectors. Ambiguities regarding the lead order are eliminated with the drawings included, below.
4) The TIS58 transistor symbol's leads in this schematic were labeled "1"
for the drain, "2" for the source, and "3" for the gate. This is contrary
to manufacturers' data, which designates pin 1 for source, pin 2 for gate,
and pin 3 for drain. Ambiguities regarding the lead order are eliminated
with the drawing included, below.
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