| 摘要 |
To facilitate the display of electrical signals derived e.g. from ultrasonic test apparatus 8,9,10, an amplifier is used which has a first gain characteristic during one part of the voltage range and a second gain characteristic during another part of the range. The amplifier may employ an operational amplifier 7 with a feedback circuit R2, R3, R4, the junction between R3 and R4 being connected to earth through a transistor 17 which becomes conductive at the transition voltage between the two characteristics as determined by the setting of a potentiometer R6. Simultaneously with transistor 17, a further transistor 18 becomes conductive and shifts the bias voltage of the amplifier by an amount determined by the setting of R7. Further network(s) 16 may provide for third ic gain characteristic(s). One or more of the characteristics may be non-linear. <IMAGE> |
