LMC6462 Datasheet, PDF (20/31 Pages) National Semiconductor (TI) – Micropower, Rail-to-Rail Input and Output CMOS Operational Amplifier

LMC6462, LMC6464
SNOS725D – MAY 1999 – REVISED MARCH 2013
www.ti.com
In Figure 52 Figure 53, R_I limits current into the amplifier since excess current can be caused by the input
voltage exceeding the supply voltage.
Precision Current Source
Figure 54. Precision Current Source
The output current I_OUT is given by:
(3)
Oscillators
Figure 55. 1 Hz Square-Wave Oscillator
For single supply 5V operation, the output of the circuit will swing from 0V to 5V. The voltage divider set up R₂,
R₃ and R₄ will cause the non-inverting input of the LMC6462 to move from 1.67V (⅓ of 5V) to 3.33V (⅔ of 5V).
This voltage behaves as the threshold voltage.
R₁ and C₁ determine the time constant of the circuit. The frequency of oscillation, f_OSC is
(4)
where Δt is the time the amplifier input takes to move from 1.67V to 3.33V. The calculations are shown below.
(5)
where τ = RC = 0.68 seconds
→t₁ = 0.27 seconds.
and
→t₂ = 0.75 seconds
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(6)
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