Lambda Diodes

The Lambda Diode, also known as a negistor, is an electronic circuit that combines a complementary pair of junction-gate field-effect transistors (JFETs) into a two-terminal device that exhibits an area of differential negative resistance (DNR) much like a tunnel diode. The term "lambda diode" refers to the shape of the device's V-I curve, which resembles the Greek letter lambda (λ).

Operation

The lambda diode operates by exploiting the inherent negative resistance characteristics of JFETs. When two JFETs are connected in a complementary configuration, their drain-current characteristics are combined in such a way that a region of DNR is created. This region of DNR occurs when the voltage across the JFETs is between the pinch-off voltages of the two devices.

Applications

Lambda diodes are used in a variety of applications, including:

• Oscillators: Lambda diodes can be used to create oscillators, which are circuits that generate a periodic waveform. The DNR of the lambda diode provides the necessary negative feedback to maintain oscillation.

• Frequency multipliers: Lambda diodes can be used to multiply the frequency of an input signal. The DNR of the lambda diode allows the device to generate harmonics of the input signal.

• Voltage-controlled resistors (VCRs): Lambda diodes can be used to create VCRs, which are devices that change their resistance in response to an applied voltage. The DNR of the lambda diode allows the device to exhibit a wide range of resistance values.

Advantages

Lambda diodes have several advantages over other types of negative-resistance devices, such as tunnel diodes:

• Higher operating voltage: Lambda diodes can operate at higher voltages than tunnel diodes. This makes them more suitable for use in high-power applications.

• Wider DNR range: Lambda diodes have a wider DNR range than tunnel diodes. This makes them more versatile and allows them to be used in a wider range of applications.

• Lower noise: Lambda diodes are generally less noisy than tunnel diodes. This makes them suitable for use in sensitive applications.

Disadvantages

Lambda diodes also have some disadvantages compared to tunnel diodes:

• Lower operating frequency: Lambda diodes typically operate at lower frequencies than tunnel diodes. This limits their use in some high-speed applications.

• Higher manufacturing cost: Lambda diodes are typically more expensive to manufacture than tunnel diodes.