> pnp/npn buffer

Of course then there is the solution of using the phototransistor as
current source into a current mirror with gain (inverts!):

  +    +
  |    |
P C    |
H E    R2
T |--  |
  C |  C-OUT
   B--B
  E    E
  |    |
  R1   |
  |    |
  GND  GND

From which the 'simulated inductance' PHT receiver is derived, which is
used for AC detection (pulsed light, also inverts):

  +         +
  |         |
P C         |
H E         R2
T |         |
  |-------  |
  C      |  C-OUT
   B---R1--B
  E  |      E
  |  C1     |
  |  |      |
  gnd gnd   gnd

Peter

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