| 摘要 |
An "all-pass" filter circuit for use, for example, as a delay section in an integrated circuit, and which should therefore be as simple and as little susceptible to production spreads as possible, comprises first and second long-tailed pairs of transistors (1, 2 and 3, 4 respectively) provided with input emitter followers (26, 28, 30, 32). The pairs are interconnected to form a gyrator having first and second ports (24 and 25 respectively). The first port is loaded by a first capacitor (17) shunted by a damping resistor (22) and the second port is loaded by a second capacitor (18). An input terminal (20) is coupled to the first port via one transistor (1) of the first pair and the relevant emitter follower (26), and the first port is coupled to an output terminal (21) via both transistors (3, 4) of the second pair and the relevant emitter follower (30). A portion of the input signal is added to the output signal in a suitable phase via a second resistor (23) which connects the emitter of the input emitter follower (20) to the emitter of the fourth, grounded-base, emitter follower (32) the collector of which is connected to the output terminal (21). The value of the second resistor is chosen so that the arrangement constitutes an "all-pass" filter circuit. If desired the collector connections of the transistors of the first pair may be interchanged provided that those of the transistors of the second pair are also interchanged. If desired the emitter followers may be omitted, the second resistor then being connected between the emitters of the first transistor (1) of the first pair and the second transistor (4) of the second pair. |
