| 摘要 |
PURPOSE:To obtain a sample/hold circuit with a wide dynamic range and a high speed of action by providing a voltage holding circuit which does not saturate a switching element to execute the changing-over control of a sampling action and a holding action. CONSTITUTION:A voltage holding circuit 9 is composed of a resistance 10 connected serially between a power source VCC and a grand terminal, a Zener diode ZD and an NPN type transistor TrQ5. During the holding period when a control signal inversion phi is an H level and phi is an L level, the input signal V1 of a low voltage level is supplied, the TrQ5 comes to be turned on, then, the current Ia conducted at a constant electric current source circuit 4 through a resistance 2 and a switching TrQ2 comes to be the total current from the resistance 2 and the TrQ5, and is conducted through the TrQ2 to the constant current source circuit 4. Thus, even when an input signal V1 comes to be further a low voltage level, the TrQ2 is hardly saturated by the current supplied from the TrQ5. |
