| 摘要 |
<p>PURPOSE:To perform stably motion or regenerative detection and to improve gain and noise figure by selecting appropriately the value of a condenser of an infinite impedance regenerative detection circuit. CONSTITUTION:The value of a condenser C1 between the source of Q2 and the ground of a circuit is 120-150PF, which is far smaller than the conventional one. Therefore, Q2, which is a high gm sharp cut-off FET, input electrostatic capacity Cin and C1 become to do an oscillation-like motion while they perform a motion of a detection circuit based on the motion principle of the Colpitts oscillation circuit. As an example, an additional gain of 6 to 9dB is obtd. and under the condition, a good noise figure with approximately at most 2dB is obtd. In an example of a fetal heart rate detector, a voltage-elevating electric source +EBB which is higher than an electric source voltage is obtd. by rectifying a carrier with a large amplitude and this is made as a drain electric source for Q2 and the dynamic range specified by the direct current motion point can be improved. In addition, the detection output is more amplified from the drain side and is extracted.</p> |
