Day 5: Everything you need to know about Activation Functions in Deep learning

Deep learning is a powerful area of ​​artificial intelligence that has received a lot of attention in recent years. One of the main components of deep learning models is the activation function. Activation functions play a crucial role in determining the output of a neural network. In this article, we will dive deep into understanding activation functions in deep learning and explore their significance in model performance and training. So, let’s get started!

What are Activation Functions?

Activation functions are mathematical functions that introduce non-linear properties to a neural network. These functions are responsible for adding non-linearity to the network, enabling it to learn and represent complex patterns in data. Activation functions are applied to the output of each neuron in a neural network, transforming the input into the desired range or form.

Activation functions help neural networks make decisions by determining whether a neuron should be activated or not based on the input it receives. They introduce non-linearity, which allows the network to approximate non-linear functions and solve complex tasks such as image recognition, natural language processing and speech recognition.

Types of Activation Functions

There are different types of activation functions used in deep learning models. Let’s discuss about some common activation functions

1. Sigmoid Activation Function

The sigmoid activation function is a widely used activation function that squashes the input into a range between 0 and 1. It has an S-shaped curve, which makes it suitable for models where the output needs to be in a probability form. The sigmoid function can be represented mathematically as:

f(x) = 1 / (1 + exp(-x))

The sigmoid function is differentiable, which makes it easy to compute gradients during backpropagation, a crucial step in training neural networks.

2. ReLU (Rectified Linear Unit) Activation Function

ReLU is one of the most popular activation functions used in deep learning models. It replaces all negative input values with zero and keeps the positive values unchanged. The mathematical representation of ReLU is:

f(x) = max(0, x)

ReLU is computationally efficient and helps in solving the vanishing gradient problem that occurs in deep neural networks. It also introduces sparsity in the network by activating only a subset of neurons.

3. Tanh Activation Function

The hyperbolic tangent (tanh) activation function is similar to the sigmoid function but squashes the input into a range between -1 and 1. The tanh function is given by:

f(x) = (exp(x) – exp(-x)) / (exp(x) + exp(-x))

Tanh is symmetric around the origin and exhibits stronger gradients for inputs compared to the sigmoid function. It is often used in the hidden layers of neural networks.

4. Softmax Activation Function

The softmax activation function is commonly used in multi-class classification problems. It takes a vector of real numbers as input and transforms it into a probability distribution over multiple class. The formula of Softmax function can be written as:

f(x) = exp(x) / sum(exp(x))

Softmax ensures that the output probabilities sum up to 1, making it suitable for multi-class classification tasks.

Why are Activation Functions Important?

Activation functions play a key role in deep learning models for the following reasons: Introducing nonlinearity: Activation functions introduce nonlinear properties into a neural network, allowing it to approximate complex functions and learn from nonlinear relationships in the data.

Enabling Complex Representations: Deep learning models with non-linear activation functions can learn and represent complex patterns and hierarchical structures present in the data.

Decision Making: Activation functions determine whether a neuron should be activated or not based on the input it receives. This decision-making capability helps the model in making accurate predictions and classifications.

Gradient Computation: Activation functions need to be differentiable to compute gradients during the backpropagation process. Gradients are essential for updating the model’s parameters and minimizing the loss function during training.


Activation functions are a fundamental component of deep learning models. They introduce non-linearity, enable complex representations, aid in decision-making, and facilitate gradient computation during model training. Understanding the different types of activation functions and their properties is important for building effective and high-performing deep learning models. By choosing the right activation function, researchers and practitioners can solve the wide range of real-world problems in deep learning.

In the next article we will be talking about each activation function in detail.

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