| 摘要 |
<p>1286202 Bi-stable and astable transistor circuits TEKTRONIX Inc 13 May 1970 [26 May 1969] 23129/70 Heading H3T The condition of a tunnel diode 16 is responsive to input current I in at 20, a load impedance 18 is connected to the input terminal 20, and a positive feedback such as T22, T32 modifies the input current in response to the current in the tunnel diode, in order to reduce hysteresis. As I in increases, tunnel diode 16 switches to the low current higher voltage condition (45, Fig. 3, not shown), and T22 collector potential goes more negative. This increases T32 collector current and the potential at 21 tends to fall, some of the current through R18 and D16 being now shunted away to T32 and the working point moving to a lower current condition (45 to 50). Thus only a small drop in I in is necessary (50 to 44) to cause the diode to switch back to the high current state (48), the positive feedback again tending to hold the operating point (48) near to the critical point (42) ready for further switching. R40 adjusts the hysteresis band by varying the low current stable point (50). If R40 is varied enough to move the low current point to the left of the peak (44), the circuit acts as an oscillator.</p> |
