STA457C

Series:	--
Packaging:	Bulk
Part Status:	Active
Transistor Type:	2 NPN, 2 PNP Darlington (H-Bridge)
Current - Collector (Ic) (Max):	4A
Voltage - Collector Emitter Breakdown (Max):	60V
Vce Saturation (Max) @ Ib, Ic:	1.5V @ 4mA, 2A
Current - Collector Cutoff (Max):	100µA (ICBO)
DC Current Gain (hFE) (Min) @ Ic, Vce:	2000 @ 2A, 4V
Power - Max:	4W
Frequency - Transition:	--
Operating Temperature:	150°C (TJ)
Mounting Type:	Through Hole
Package / Case:	10-SIP
Supplier Device Package:	10-SIP

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STA457C application field and working principle

The STA457C is a switching regulator subcircuit of bipolar transistors in an array. It has a wide range of applications, including low-voltage regulation, high-current regulation and various other power control functions. The STA457C can be used as a dual-rail power supply, and also as an adjustable current source for precision voltage regulation.The basic structure of the STA457C is a four-transistor array. The four transistors are connected to form a parallel current-mirror circuit, and the collector current of each transistor is mirrored onto the base of the next transistor along. The result is a self-regulating cycle, such that when a load is connected to one of the output terminals, the voltage across the load is regulated.In order to understand the full operation of the STA457C, it is necessary to look at the details of the circuit. The four transistors are arranged in two parallel sets of two. The first set consists of an NPN-type and PNP-type transistor, which are connected in a current-mirror configuration with their bases and emitters connected to one another. The second set of two transistors are also connected in a similar way, however, the base of the PNP-type transistor is connected to the collector of the NPN-type transistor and the collector of the PNP-type transistor is connected to the base of the NPN-type transistor. This arrangement gives the circuit its self-regulating properties.When a load is connected to one of the output terminals, current will flow from the power supply to the collector of the PNP-type transistor, and from there to the base of the NPN-type transistor. The NPN-type transistor will then begin to conduct and begin to mirror the current from the PNP-type transistor onto the base of the opposite NPN-type transistor. This process will continue until the output voltage is regulated to the desired level.The STA457C is a very useful component in a variety of applications. It is capable of providing a stable, regulated voltage, even when subjected to large changes in load and temperature, which is important in low-voltage applications. It can also be used as a dual-rail power supply, and since the two output rails are independent, both are regulated independently. Furthermore, the STA457C can also be used as an adjustable current source, which is useful for precision voltage regulation.Overall, the STA457C is a versatile component for a variety of power-supply regulation and current-control applications. Its self-regulating properties, dual-rail power supply capability and adjustable current-source capabilities make it suitable for use in all types of applications.

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