| 摘要 |
An integrated circuit including a resistor that at least partially overlies a first tub of semiconductor material of a first polarity, where the first tub is formed in a second tub of semiconductor material having the opposite polarity, and the second tub is formed in a semiconductor substrate having the first polarity. The second tub forms the base of a vertical bipolar transistor, the first tub forms the emitter of the transistor, and the substrate forms the collector of such transistor. Where the vertical transistor is a PNP transistor, the first tub is the emitter and consists of P-type semiconductor material, the second tub is the base, and the substrate is the collector. Preferably, the resistor is a strip of polysilicon or a set of multiple, series-connected polysilicon segments. Typically, the integrated circuit is an amplifier and the resistor is a gain-setting resistor. In some embodiments, the resistor extends between a first node and a second node (whose potential varies in response to changes in the input signal), and the resistor is implemented with double bootstrapping, in the sense that the first tub is coupled to a third node of the integrated circuit whose potential changes (in response to a change in the input signal) in such a direction as to pull the potential at the second node in a desired direction and the second tub is coupled to a fourth node whose also potential changes (in response to a change in the input signal) in such a direction as to pull the potential at the second node in a desired direction, without significant current leakage from the first tub to the substrate. For example, the integrated circuit can be (or include) a high-speed cascode amplifier, the third node can be the amplifier's output node, and the fourth node can be the base of a bipolar transistor of a cascode Darlington push-pull output stage of the amplifier.
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