Ultra Low Voltage Crystal Oscillator Circuit Using Active Loads

 This is an ultra low-voltage crystal Oscillator circuit using EPAD MOSFETs with active load and output Buffer
This circuit is similar to a standard crystal Oscillator circuit used in 5V circuits. However, at low operating
voltages, the values of the resistors and the impedance of the inverter MOSFET are selected to optimize
oscillation stability and minimize power consumption. An active load device using a depletion mode EPAD
MOSFET such as an ALD114804 replaces a passive resistor load at the inverter.  Using appropriate component
values, a crystal Oscillator circuit CAN be configured to operate in the range of supply voltages from V+ = 5V
to V+ = 0.5V, with crystal frequencies ranging from 1 MHz to 16 MHz. The active load reduces the contrast in
the corresponding power consumption at different supply voltages. At V+= 5V the power consumed by the
oscillator circuit is 346 µW whereas at V+= 0.5V, the same circuit consumes a mere 32 µW while oscillating at
the same selected crystal frequency. At higher crystal frequencies in excess of 4 MHz, a dual EPAD MOSFET
can be connected in parallel to provide more low voltage drive current necessary.
Recommended Components
EPAD MOSFETs: M1, M3 ALD110800 (either single or dual MOSFET connected in parallel);
Active Load: M2 ½ ALD114904  
CL1=10pF;  CL2 = 22pF;  RF= 5.6MOhm;  RL= 6 Ohm;  ROUT = 2.4KOhm
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Ultra Low Voltage Crystal Oscillator Circuit Using Active Loads application circuits
Ultra Low Voltage Crystal Oscillator Circuit Using Active Loads application circuits



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