Generating Square Waves: A Fundamental Oscillator
A squarewave generator, essentially an oscillator, operates autonomously, delivering output without requiring any initial input, except for a momentary impulse input within zero seconds. This unique characteristic makes it indispensable in digital signal processing and various electronic applications where precise timing and pulsating signals are essential.
Innovative BiMOS Opamps for Versatile Applications
Texas Instruments has introduced a new series of BiMOS opamps, ranging from TLC070 to TLC075, designed specifically for instrumentation, audio, and automotive applications. This oscillator stands as a prime example of their capabilities. Capable of generating stable and highly accurate square waves at frequencies up to 60 kHz, it showcases an impressive output current range of ±30 mA, making it a valuable tool in applications demanding low noise, high speed, and minimal distortion.
Utilizing TLC073 Dual Opamp with Shutdown Function
In this circuit, the TLC073, a dual opamp featuring a shutdown function, is employed. IC1a is configured as a conventional square wave generator, while IC1b serves as the driver. The oscillation frequency is determined by Cx and Rx and is calculated for frequencies up to 20 kHz.
Frequency Control and Stability
The provided table presents preferred values leading to different frequencies. It’s crucial to note that the frequency variation is primarily influenced by the capacitor since Rx must always be significantly larger than the feedback resistor R3. The impact of the supply voltage, rated at –130 dB, is remarkably small, and the frequency’s temperature coefficient is a mere 1.5%. Beyond 20 kHz, the oscillator remains stable but exhibits increased non-linearity.
Customizable Mark-Space Ratio
The mark-space ratio of the output signal can be adjusted within the 10% to 90% range by modifying the ratio of resistors R1 to R2. When the two resistors are equal, the output becomes symmetrical. The driver’s output fluctuates between +0.3 V (low) and 1 V below the supply voltage (high).
Controlling the Oscillator
The operation of the oscillator can be toggled on and off by utilizing the shutdown input of IC1a. When engaged, the opamp’s output shifts to high impedance, leading to a significant drop in current consumption, reaching as low as 35 nA.
Comparing with Common TL071
Alternatively, the oscillator can be constructed using the standard TL071 (with Ub=7 V, Uout=1.2/6.2 V, Iout=1.75 mA, fmax=50 kHz). However, it’s worth noting that the TL071 possesses a lower output drive capability, as evident from its specifications.
Introduction to TL071
The TL071 is classified as a high-speed JFET input single operational amplifier. It combines well-matched, high-voltage JFET and bipolar transistors within a monolithic integrated circuit, making it a versatile choice for various electronic applications.