Phantastron

Description: A relaxation oscillator that produces linearly varying voltage with a low nonlinear distortion factor. Phantastrons can function in either slave or self-oscillating modes. Phantastrons designed for large variable voltage ranges (tens to hundreds of volts) typically utilize electron tubes, such as pentodes or pentagrid tubes, while those with smaller voltage ranges employ bipolar or unipolar field-effect transistors. Solid-state phantastrons are referred to as phantastrans. The operating cycle of a phantastran is divided into four stages: quiescent, triggered, operating, and regeneration. In the quiescent stage, transistor T1 is saturated, T3 is near saturation, and T2 is turned off. The circuit diagram of a solid-state phantastron includes components such as resistors (R), capacitors (C), a potentiometer (P), transistors (T), a diode (D), a power supply (Ec), and a triggering pulse (TP). The triggering pulse, initiated by a negative voltage pulse, passes through capacitors C3, D, and C to the base of T3, activating it. Once triggered, T1 is turned off and T2 is enabled. During the operating stage, capacitor C discharges almost linearly until the voltage at the collector of T2 reaches a critical value (approximately 12 V). At the conclusion of the operating stage, T1 is enabled and saturates due to the subsequent regeneration process, while T2 is turned off. In the regeneration stage, capacitor C is charged by the power supply through resistor R3 and the base of T3. The duration of the regeneration stage is defined as r = 3R3C. The duration of the operating stage, which determines the length of the generated pulses, varies with circuit parameters, ranging from several microseconds to several tens of seconds. The pulse length can be adjusted continuously using potentiometer P or in discrete increments via capacitor C. In radio applications, phantastrons are utilized for fine-tuning time delays, functioning as sawtooth generators, and generating long rectangular pulses. A variant of the phantastron is known as the sanatron.

The phantastron circuit is an important component in various electronic applications, particularly in timing and pulse generation. The design focuses on minimizing nonlinear distortion while allowing for a wide range of output voltages. The use of both electron tubes and solid-state components enables flexibility in application, catering to different voltage requirements and performance characteristics.

The quiescent stage is critical for establishing the initial conditions of the circuit, ensuring that T1 is saturated, which allows for rapid response when triggered. The triggering mechanism is essential for initiating the oscillation process, where the negative voltage pulse serves to activate T3, leading to a swift transition in the state of T1 and T2. The linear discharge of capacitor C during the operating stage is a hallmark of the phantastron design, promoting a predictable and stable output waveform.

The regeneration stage is particularly significant as it recharges the capacitor, preparing the circuit for the next cycle of operation. The relationship between the resistor R3 and capacitor C defines the timing characteristics of the circuit, allowing for precise control over pulse duration. This feature is invaluable in applications requiring accurate timing, such as in pulse modulation and signal processing.

The versatility of phantastrons extends to their use in fine-tuning applications within radio devices, where precise timing and waveform shaping are essential for optimal performance. The ability to generate both sawtooth and rectangular pulses makes phantastrons suitable for a variety of signal generation tasks, enhancing their utility in electronic design. The sanatron variant further expands the functionality of phantastrons, offering alternative configurations for specific application needs.a relaxation oscillator of linearly varying voltage with a low nonlinear distortion factor. Phantastrons may operate in a slave or self-oscillating mode. Phantastrons with large ranges of variable voltage (tens or hundreds of volts [V]) use electron tubes, usually pentodes or pentagrid tubes; those with smaller ranges use bipolar or unipolar field -effect transistors. Solid-state phantastrons are called phantastrans. Figure 1 shows a circuit diagram of a solid-state phantastron, or phantastran. The complete operating cycle of the phantastran is divided into quiescent, triggered, operating, and regeneration stages. In the quiescent stage, T1 is saturated, T3 is on the threshold of saturation, and T2 is cut off. A phantastran of this type is Figure 1. Circuit diagram of a solid-state phantastron or phantastran: (R) resistors, (C) capacitors, (P) potentiometer, (T) transistors, (D) diode, (Ec) power supply, (TP) triggering pulse triggered by a negative voltage pulse that passes through C3, D, and C, arrives at the base of T3, and activates T3; after the device is triggered, T1 is cut off and T2 is enabled.

An almost linear discharge of the capacitor C occurs during the operating stage, which ends when the potential at the collector of T2 reaches some critical value (1 2 V). At the end of the operating stage, T1 is enabled and becomes saturated as a result of the ensuing regeneration process, while T2 is cut off.

During the regeneration stage, C is charged by the power supply through R3 and the base of T3. The duration of the regeneration stage is r = 3R3C. The duration of the operating stage, that is, the length of the generated pulses, depends on the circuit parameters and ranges from several microseconds to several tens of seconds. The pulse length can be continuously controlled by a potentiometer P or in discrete increments by the capacitor C.

In radio devices, phantastrons are used for the fine tuning of time delays, as sawtooth generators, and to generate long rectangular pulses. A variant of the phantastron is the sanatron.