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| View Original: | Neon bulb relaxation oscillator hysteresis curve 2.svg (1034x1799) | |||
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| Keywords: Neon bulb relaxation oscillator hysteresis curve 2.svg characteristic curve of a neon bulb relaxation oscillator top showing the hysteresis loop abcd of the oscillation and the resulting output voltage waveform bottom A neon bulb relaxation oscillator consists of a capacitor which is charged from a voltage source V<sub>0</sub> through a resistor R<sub>2</sub> with a neon bulb across the capacitor which discharges it once it reaches the bulb's breakdown voltage V<sub>b</sub> Ths hysteresis curve abcd shows the detailed cycle a-b The voltage across the bulb rises slowly from zero as the capacitor charges through a to b where it reaches the breakdown voltage V<sub>b</sub> of the bulb The gas in the bulb ionizes and it become conductive b-c The charge from the capacitor begins to flow through the bulb instantly increasing the current to point b in the abnormal glow region of the curve The bulb turns on c-d The voltage across the bulb and capacitor drops quickly to the extinguishing voltage V<sub>e</sub> at which the voltage is insufficient to continue ionizing the gas d-a The current through the bulb drops to a very low level and the bulb turns off This allows the current from the resistor R<sub>1</sub> to begin charging the capacitor up again from a to b and the cycle repeats The circuit generates a sawtooth wave bottom alternating between V<sub>e</sub> and V<sub>b</sub> The center blue line is the load line with a slope equal to the resistance R<sub>2</sub> In order for the circuit to oscillate the load line must intersect the IV curve in it's negative resistance region <font color red > red </font> the segment from b to d where it is declining to the right If the resistor has too large a value shown by line R<sub>3</sub> so the load line intersects the curve in section a-b the resistor current will be so low that the bulb leakage current will bleed the capacitor charge away and the voltage will never reach V<sub>b</sub> If the resistor is too small so the load line intersects the curve in section c-d shown by line R<sub>1</sub> the current through the resistor will be large enough to keep the bulb turned on and it won't reach the extinguishing voltage V<sub>e</sub> Information from http //www introni it/pdf/GE 20Glow 20Lamp 20Manual pdf C R Daugherty et al General Electric Glow Lamp Manual 2nd Ed General Electric Cleveland Ohio 1966 2014-04-02 07 23 26 own Chetvorno Neon bulb relaxation oscillator hysteresis curve svg cc-zero Uploaded with UploadWizard Negative resistance Device current-voltage characteristics Relaxation oscillators | ||||
