| 摘要 |
<p>An amplifier circuit comprises first and second gain cells (18A, 18B) connected in cascade. Each of the gain cells comprises first and second common emitter differential transistors (30A, 32A; 30B, 32B), a current source (44) coupled to the emitters of the transistors, a first plurality of forward biased, series diodes (34A - 37A) connected between a power supply terminal (40) and a base of the first transistor (30A), and a second plurality of forward biased, series diodes (64A - 67A) connected between the power supply terminal (40) and a base of the second transistor (32A). A collector of the first transistor (30A) of the first gain cell (18A) is connected to the base of the first transistor (30B) of the second gain cell (18B), and a collector of the second transistor (32A) of the first gain cell (18A) is connected to the base of the second transistor (32B) of the second gain cell (18B). Because of the low inherent resistance of the biasing diodes, the operating speed of the amplifier is large, and the current amplification can be large without exceeding the power supply voltage. The current source limits the gain for high level signals without causing saturation of the transistors and therefore, does not comprise operating speed. The gain of each cell equals the numbers of diodes connected to the base of the transistor until the level of the current source. <IMAGE></p> |
