LMV321-N, LMV321-N-Q1, LMV358-N, LMV358-N-Q1
LMV324-N, LMV324-N-Q1
SNOS012I –AUGUST 2000–REVISED FEBRUARY 2013
www.ti.com
Figure 67 is a squarewave generator with the same path for charging and discharging the capacitor.
Figure 67. Squarewave Generator
CURRENT SOURCE AND SINK
The LMV321-N/LMV358-N/LMV324-N can be used in feedback loops which regulate the current in external PNP
transistors to provide current sources or in external NPN transistors to provide current sinks.
Fixed Current Source
A multiple fixed current source is shown in Figure 68. A voltage (VREF = 2V) is established across resistor R3 by
the voltage divider (R3 and R4). Negative feedback is used to cause the voltage drop across R1 to be equal to
VREF. This controls the emitter current of transistor Q1 and if we neglect the base current of Q1 and Q2,
essentially this same current is available out of the collector of Q1.
Large input resistors can be used to reduce current loss and a Darlington connection can be used to reduce
errors due to the β of Q1.
The resistor, R2, can be used to scale the collector current of Q2 either above or below the 1 mA reference value.
Figure 68. Fixed Current Source
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