| 摘要 |
PURPOSE:To form the circuit without use of an inductor by forming a filter section as an active filter consisting of a passive circuit section and a voltage buffer. CONSTITUTION:A filter section 7 has a 2nd-order active low pass filter of Sallen-key type. That is, the input terminal of a voltage buffer 8 is connected to the collector of a transistor(TR) 3 via a resistor 9 and connected to the emitter of the TR 3 via a capacitor 10 and a resistor 11 and the output terminal of the voltage buffer 8 is connected to the collector of the TR 3 via a capacitor 12 to apply positive feedback. Then a passive circuit section 7a is constituted of the resistor 9, the capacitors 10, 12 and the resistor 4. Thus, the circuit is formed without use of an inductor and the constitution is suitable for circuit integration of the circuit, and various disadvantages caused by using the inductance to the filter section are avoided. |
