- on Audio & music
- Published in issue 7/1989 on page 42
Lc Sine Wave Generator
C Z 70n R2 U D1 02 LT V I 180n ‚Ä¢‚Ä¢ 470 p H 065 TEST & MEASUREMENT =Ma 560p 6n8 =On C4 5 270n 1I0In LC SINE WAVE GENERATOR R33c1 100nH...10H BS170 17n8 0 5V This compact LC oscillator offers a frequency range of about 1 kHz to almost 9 MHz and a low-distortion sine wave output. The heart of the circuit is series-resonant circuit Ll-C2-C3 in the feedback loop of amplifiers T1 -T2. Transistor T2, which is connected as an emitter follower, serves as impedance converter, whereas T1, connected in a common base circuit, is a volt- age amplifier whose amplification is determined by the impedance of Ll in its col- lector circuit and the emitter current. The feedback loop runs from the collector of T1 via the junction of capacitive divider Cl -C2, source follower BS170 and the input impedance formed by R1 and C4. The whole is strongly reminiscent of a Colpitts circuit. The signal is also taken to the output terminal via C5. Of particular interest is the amplitude control by the current s...