A previous Design Idea describes a programmable current source that used a three-terminal National Semiconductor LM317 adjustable regulator (Reference 1). Although that circuit lets you program the output current, the load current flowed through the…

Industrial controls make heavy use of 4- to 20-mA current loops to transmit process measurements because current loops retain information in the presence of noise and changes in loop voltage. The loop circuit requires proper calibration to ensure acc…

对一个互补输出的驱动器而言,从输出端向外电路流出的负载电流称为拉电流(SOURCE CURRENT):从外电路流入输出端的负载电流称为灌电流(SINK CURRENT):在没有负载的情况下,驱动器本身消耗的电流称为QUIESCENT CURRENT.对于拉电流的理解:例如一个5V的驱动器的输出端(假设为推挽输出),该端子悬空时,输出"H"的电压为0.9*VDD=4.5V以上,输出"L"的电压为0.1*VDD=0.5V以下.如果在这个输出端加一个阻性负载到地,这时输出…

http://java.inf.elte.hu/java-1.3/javacard/iso7816.txt ============================================================================= ISO7816 (part 1-3) asynchronous smartcard information ================================================================…

Dual-polarity supply provides ±12V from one IC VC (Pin 1): Error Amplifier Output Pin. Tie external compensation network to this pin or use the internal compensation network by shorting the VC pin to the COMP pin.External compensation consists of pla…

The popular USB interface can charge a portable device while transferring data. But for high-capacity batteries, the 500-mA output current of USB hosts and powered hubs greatly extends the charging time. (Unpowered USB hubs supply no more than 100 mA…

Targeting use in portable-system applications that require raising a battery's voltage to a higher level, IC boost regulators often include output transistors that can drive storage inductors. However, most boost regulators' absolute-maximum input-vo…

LDO current regulator for power LED Challenge You've got a power LED? Great! Build a flash light! What does the spec say? "Voltage: 3.6 .. 3.8 V, power 3 W." Okay. This means that it draws some 800 mA. Three mignon cells give 4.5 V for at least…

The USB (Universal Serial Bus) specification requires a connected USB device to present a load to the host or hub of no greater than 10 µF in parallel with 44Ω, including the effects of any bypass capacitance visible through the device’s voltage regu…

The circuit in Figure 1 uses a minimal number of external parts to raise the maximum output current of a 0.5A buck switching-regulator IC to more than 6A. The circuit accommodates input voltages of 15 to 60V and delivers output voltages of 3.3, 5, or…