Voltage Divider Calculator
Calculate voltage divider output voltage, current, Thévenin impedance, and power dissipation from Vin, R1, and R2. Ideal for bias networks and level shifting.
Formula
V_{out} = V_{in} \cdot \frac{R_2}{R_1 + R_2}
How It Works
A voltage divider is a fundamental passive circuit topology used to reduce voltage levels linearly by utilizing two resistors connected in series. When a voltage is applied across the two resistors, the output voltage appears at the connection point between them, proportional to their resistance values. This principle relies on Ohm's Law and the basic electrical property that current remains constant through series resistors while voltage is distributed according to each resistor's resistance. The voltage division ratio depends on the relative values of R1 and R2, allowing precise scaling of input voltages with minimal complexity. By selecting appropriate resistor values, engineers can condition signals, create reference voltages, and interface circuits with different voltage requirements.
Worked Example
Consider a 5V input voltage with R1 = 1000 Ω and R2 = 2000 Ω. Calculating the output voltage: Vout = 5V · (2000 Ω) / (1000 Ω + 2000 Ω) = 5V · (2/3) = 3.33V. The Thevenin equivalent resistance would be R1 || R2 = (1000 Ω · 2000 Ω) / (1000 Ω + 2000 Ω) = 666.67 Ω. If we then load this circuit with a 10 kΩ load resistor, the loaded output voltage becomes Vout_loaded = 5V · (2000 Ω || 10000 Ω) / (1000 Ω + (2000 Ω || 10000 Ω)) = 2.27V, demonstrating the significant loading effect.
Practical Tips
- ✓Use 1% tolerance resistors for more precise voltage division
- ✓Consider thermal effects and power dissipation in high-current applications
- ✓Add bypass capacitors to reduce noise in sensitive analog circuits
Common Mistakes
- ✗Neglecting load resistance impact on output voltage accuracy
- ✗Using resistors with high tolerance in precision voltage division
- ✗Overlooking power dissipation limits of selected resistors
Frequently Asked Questions
What is the maximum current through a voltage divider?
Maximum current is determined by the total resistance and input voltage, following Ohm's Law. Always ensure the current doesn't exceed component ratings.
Can voltage dividers work with AC signals?
Yes, voltage dividers work identically with AC signals, though capacitive and inductive effects become more significant at higher frequencies.
How do I choose resistor values?
Select resistor values to achieve desired voltage ratio while maintaining sufficiently low current to minimize power consumption and loading effects.
What is the input impedance of a voltage divider?
The input impedance is the parallel combination of R1 and R2, which affects circuit loading and signal transmission characteristics.
Can I use voltage dividers for level shifting?
Voltage dividers are excellent for converting between different voltage domains, such as shifting 5V logic to 3.3V logic in mixed-voltage systems.
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