The Circuit Design Blog

Voltage-Controlled Electronic Load circuit:

This circuit is a voltage-controlled current sink.

It is scaled to provide a 500mA output current with a +1V input voltage.

This type of current sink can be very useful in power supply testing applications.

A R-R output op amp with an input common-mode range that includes its negative supply rail,  such as an OPA251, is required for single- supply operation.

Re- scaling this circuit with other Darlington transistors or low- threshold N-channel MOSFETs can result in an output current sink capability of many amps.

(Circuit is created by Neil P. Albaugh,  TI – Tucson)

Voltage-Controlled Electronic Load circuit:

Online Simulation of the Voltage-Controlled Electronic Load Circuit

The great feature of the TINA circuit simulator that you can analyze this circuit immediately with TINACloud the online version of TINA. Of course you can also run this circuit in the off-line version of TINA.

Click here to invoke TINACloud  and analyze the circuit yourself, or watch our tutorial video! 

You can send this link to any TINACloud customers and they can immediatelly load it by a single click and then run using TINACloud.

Michael Koltai
www.tina.com

Differential Amplifier Resistor Tolerance Analysis

Make all resistors “Control Objects” and use “Parameter Stepping” to step each resistor value from 9.9k (1% low) to 10.1k (1% high) in 3 linear steps. Run DC Analysis, “DC Transfer Characteristic” and sweep “Vcmv” from -1V to +1V. The resulting family of curves shows the differential amplifier output error due to the various resistor tolerance combinations. The OPA277 error contribution is nil. Note that using 1% resistors in a differential amplifier design can result in a worst- case CMRR error of 20mV per volt of common-mode voltage. This is only 36dB! (Circuit is created Neil P. Albaugh  TI-Tucson)

Differential Amplifier Resistor Tolerance Analysis Circuit:

Online Simulation of the Differential Amplifier Resistor Tolerance Analysis Circuit

The great feature of the TINA circuit simulator that you can analyze this circuit immediately with TINACloud the online version of TINA. Of course you can also run this circuit in the off-line version of TINA.

Click here to invoke TINACloud  and analyze the circuit yourself, or watch our tutorial video! 

You can send this link to any TINACloud customers and they can immediatelly load it by a single click and then run using TINACloud.

Michael Koltai
www.tina.com

Positive Output Precision Voltage Limiter

This circuit limits its output to a positive- going output only; negative output is clamped to ground. For negative inputs, D1 conducts and R2 provides negative feedback into U1’s summing junction. For positive inputs, D2 conducts and holds the summing junction to 0V. Thus the output across RL can only be positive. This characteristic is handy when driving single-supply amplifiers or unipolar A/D converters. For a negative output simply reverse D1 & D2. As shown, this circuit is a unity- gain inverter but it is also capable of providing voltage gain. Av = – 2 / R1. (Circuit is created by Neil P. Albaugh,  TI – Tucson)

Positive Output Precision Voltage Limiter circuit:

Online Simulation of the Positive Output Precision Voltage Limiter Circuit

The great feature of the TINA circuit simulator that you can analyze this circuit immediately with TINACloud the online version of TINA. Of course you can also run this circuit in the off-line version of TINA.

Click here to invoke TINACloud  and analyze the circuit yourself, or watch our tutorial video! 

You can send this link to any TINACloud customers and they can immediatelly load it by a single click and then run using TINACloud.

Michael Koltai
www.tina.com

Online Simulation of a Transimpedance Amplifier Circuit

This fast photodiode transimpedance amplifier is based on a high- speed JFET- input op amp OPA657.

This op amp is compensated for a minimum closed- loop gain of 7V/V, but the capacitance of the photodiode plus the op amp input capacitance together with the feedback resistor R1 provides a noise gain at high frequency that allows stable operation.

Compensation capacitor C1 optimizes the amplifier bandwidth / gain peaking tradeoff.

Achieving this level of performance requires very careful layout and the circuit must be shielded to prevent noise pickup.

(Circuit is created by Neil P. Albaugh,  TI- Tucson)

Transimpedance amplifier circuit:

Online Simulation of a Transimpedance Amplifier Circuit

The great feature of the TINA circuit simulator that you can analyze this circuit immediately with TINACloud the online version of TINA. Of course you can also run this circuit in the off-line version of TINA.

Click here to invoke TINACloud and analyze the circuit yourself, or watch our tutorial video!  

You can send this link to any TINACloud customers and they can immediatelly load it by a single click and then run using TINACloud.

Michael Koltai
www.tina.com

Comparator Window Settings

Conventional window comparators suffer interaction between the width and the center of the window.

This makes adjusting these parameters time consuming.

By using a precision dual 100uA current reference (REF200), this interaction is eliminated.

The width of the comparator window is determined by the reference current and the value of P1: V = 100uA * 20k.

The DC voltage of the window center is set by the % rotation of the potentiometer P1.

With the pot at its center (50%), the center of the comparator window is at zero volts– thus the window is +/-1V. The window center adjustment is illustrated below. (Circuit is created by Neil P. Albaugh  TI- Tucson)

Comparator Window Settings circuit:

Online Simulation of the Comparator Window Settings Circuit

The great feature of the TINA circuit simulator that you can analyze this circuit immediately with TINACloud the online version of TINA. Of course you can also run this circuit in the off-line version of TINA.

Click here to invoke TINACloud and analyze the circuit yourself, or watch our tutorial video!  

You can send this link to any TINACloud customers and they can immediatelly load it by a single click and then run using TINACloud.

Michael Koltai
www.tina.com