Bipolar junction transistor (BJT)--resonant tunneling diode (RTD) oscillator circuit and method

An oscillator circuit comprising:

• a ground terminal;
• a supply terminal;
• an output terminal;
• an npn bipolar junction transistor (BJT) having a base, a collector connected to said output terminal, and an emitter;
• an inductor that is connected between said ground terminal and said BJT's emitter;
• and
• a resonant tunneling diode (RTD) that is connected between said supply terminal and said BJT's collector, said RTD having a characteristic I-V curve that has positive and negative differential resistance regions that respectively lie at voltage levels below and above a peak voltage level V.sub.P,
• supply and bias voltages respectively applied at said supply terminal and the base of said BJT biasing said RTD at a DC operating point (I.sub.Q,V.sub.Q) on its characteristic I-V curve in its negative differential resistance region and forward biasing said BJT so that its average collector current is approximately equal to the current I.sub.Q at the DC operating point, said RTD producing a negative resistance seen looking into said BJT from said output terminal, the thermal noise inherent in said BJT causing said oscillator circuit to start oscillating about the DC operating point (I.sub.Q,V.sub.Q) where the RTD's negative differential resistance provides positive feedback that amplifies the oscillations until equilibrium is established, thereby producing a sinusoidal waveform at an oscillation frequency that is a function of said inductor at said output terminal.

A method of providing an oscillating waveform, comprising:

• providing an oscillator circuit, comprising:
• a ground terminal;
• a supply terminal;
• an output terminal;
• an npn bipolar junction transistor (BJT) having a base, a collector connected to said output terminal, and an emitter;
• an inductor that is connected between said ground terminal and said BJT's emitter;
• and
• a resonant tunneling diode (RTD) that is connected between said supply terminal and said BJT's collector, said RTD having a characteristic I-V curve that has positive and negative differential resistance regions that respectively lie at voltage levels below and above a peak voltage level V.sub.P ;
• selecting a DC operating point (I.sub.Q,V.sub.Q) in the RTD's negative differential resistance region;
• applying a bias voltage to the base of the BJT to forward bias the BJT so that its average collector current is approximately equal to the current I.sub.Q flowing through the RTD at the selected DC operating point, said RTD producing a negative resistance seen looking into said BJT from said output terminal;
• and
• applying a supply voltage to the supply terminal that sets the DC voltage across the RTD equal to the voltage V.sub.Q at the selected DC operating point,
• the thermal noise inherent in said BJT causing said oscillator circuit to start oscillating about the DC operating point (I.sub.Q,V.sub.Q) where the RTD's negative differential resistance provides positive feedback that amplifies the oscillations until equilibrium is established, thereby producing a sinusoidal voltage waveform at an oscillation frequency that is a function of said inductor at said output terminal.