Random number generating circuit
View Patent ↗Provided is a random number generating circuit having a simple circuit structure, for generating a physical random number based on a noise. The random number generating circuit includes a reference voltage section, an inverting amplifier section having a threshold voltage equal to a reference voltage level, and a semiconductor switch provided between an output terminal of the reference voltage section and an input terminal of the inverting amplifier section. A thermal noise produced from the reference voltage section is held by the semiconductor switch and a capacitor and amplified by the inverting amplifier section to generate the physical random number.
1. A random number generating circuit, comprising:
a reference voltage section consisting of:
a first P-channel MOS transistor having a source connected with a power supply, and a gate and a drain connected with each other; and
a first N-channel MOS transistor having a source grounded, and a gate and a drain which are connected with each other, the drain being connected with the drain of the first P-channel MOS transistor;
an inverting amplifier section consisting of:
a second P-channel MOS transistor having a source connected with the power supply; and
a second N-channel MOS transistor having a grounded source, a gate connected with a gate of the second P-channel MOS transistor, and a drain connected with a drain of the second P-channel MOS transistor, wherein the drain of the second P-channel MOS transistor outputs the generated random number; and
a semiconductor switch operating at a frequency compatible with the response speed of the inverting amplifier section, the switch including a first terminal connected with the drain of the first P-channel MOS transistor and a second terminal connected with the gate of the second P-channel MOS transistor, and further including a capacitor coupled to the second terminal and storing a sampling voltage, such that the sampling voltage is provided to the inverting amplifier section.
2. A random number generating circuit according to claim 1 , wherein the reference voltage section has a reference voltage equal to a logic threshold voltage of the inverting amplifier section.
3. A random number generating circuit according to claim 1 , wherein: the first P-channel MOS transistor and the second P-channel MOS transistor have transistor sizes equal to each other; and the first N-channel MOS transistor and the second N-channel MOS transistor have transistor sizes equal to each other.
4. A random number generating circuit according to claim 1 , wherein the semiconductor switch comprises a transfer gate including a MOS transistor, and wherein the MOS transistor is sized such that the on/off state of the MOS transistor is responsive to a signal frequency of less than 100 kHz.