The disclosed amplifier includes first and second transistors each having an emitter coupled to a bias source, a base, a first collector and a second collector. A third transistor has a collector connected to another bias source, an emitter connected to the base of the first transistor and to the first collector of the second transistor, and a base for receiving input signals. A fourth transistor has a collector connected to another bias source, an emitter connected to the base of the second transistor and to the first collector of the first transistor, and a base for receiving second input signals. Any difference in voltage between the input signals is indicated by an imbalance in current through the second collectors of the first and second transistors. The first collectors of these transistors provide positive feedback for amplifying the magnitude of this imbalance.
A variable gain amplifying circuit is disclosed, which comprises a first transistor pair whose bases are connected to input terminals, a PN junction pair with bias currents that are collector currents of the first transistor pair, a second transistor pair with a common emitter that is a base input of a voltage difference of the PN junction pair, the common emitter having a current source, and a third transistor pair whose collectors are connected to corresponding emitters of the first transistor pair, whose bases are connected to the corresponding collectors, whose emitter are connected through a resistor, and whose emitters are connected to a current source for supplying bias currents, wherein outputs are obtained from the collector of the second transistor pair.
A solid state current sensing circuit which is useful in a power supply has bipolar as well as CMOS transistors. The bipolar transistors serve as output transistors and have lateral collectors as well as substrate collectors. The lateral collectors of the bipolar transistors are used to sense a portion of the current carried by the substrate collectors. The lateral collectors are connected to a current mirror which provides an output indication of when the output current exceeds a predetermined amount. The entire circuit can be integrated on a single chip.
A driving circuit for a two-phase brushless motor which includes a magnetized rotor, first and second magnetically sensitive elements disposed adjacent the rotor, and a pair of driving coils. The magnetically sensitive elements are coupled in series with one another and a bias voltage is applied thereto. First and second differential pairs of transistors receive inputs from the first and second magnetically sensitive elements, respectively, and the first and second differential pairs are coupled in series with one another and a constant current is applied thereto. Current mirror circuits produce currents in proportion to the currents flowing in the first and second differential pairs and output drivers energize the coils of the motor in response to outputs of the current mirror circuits.
A voltage controlled element includes first and second pairs of transistors where bases of two of the transistors are connected to a reference voltage and bases of the remaining two transistors are connected to a control signal, emitters of transistors of respective pairs are connected together, differences in collector currents between transistors of said pairs define output signals from said element, including feedback means for providing as a portion of a signal input to means for drawing currents from said connected emitters signal outputs of said element.
An operational amplifier having an extremely high gain-bandwidth product. The amplifier includes a gain cell with an active negative resistance circuit made up of two matched NPN transistors (18 and 20) with their bases cross-connected to their collectors, and with a differential pair of NPN transistors (14 and 16) having their emitters degenerated through the active negative resistance circuit. The value of the negative resistance is chosen to negate other resistance values in the denominator of a fraction expressing overall amplifier gain, which is therefore maximized. Since no PNP transistors are needed to maximize gain in the amplifier, NPN transistors can be used exclusively, and the amplifier can be more conveniently fabricated in integrated-circuit form, with a desirably wide bandwidth.
